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COPYRIGHT DEPOSIT. 



















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Fig. 24. Complete arc installation on shipboard 

























RADIO 


A PRACTICAL MANUAL WITH 
QUESTIONS AND ANSWERS 


BY 

JOHN R. IRWIN 



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NEW YORK 

EDWARD J. CLODE 







TKtoSSa 

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Copyright, 1922 , by 
Edward J. Clode 



PRINTED IN THE UNITED STATES OF AMERICA 



JUL 17 1922 


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CONTENTS 


CHAPTER PAGE 

I. Early Days of Radio ...... 1 

II. Elementary Electricity ... 11 

III. Magnetism and Electro-Magnetism 45 

IV. Explanation of Radio .... 58 

V. Practical Radio Telegraphy . . 64 

VI. Radio Reception. 109 

VII. Vacuum Tubes in Radio .... 127 

VIII. Radio Telephony. 151 

IX. Antenna. 156 

X. Definition.• . . 165 

XI. Questions and Answers . . . 192 

XII. How to Build a Simple Receiver . 210 

APPENDICES 

I. Fire Protection Regulations . . 228 

II. United States and International 

Radio Regulations. 234 

Bibliography. 251 

Radio—God's Wonderful Gift to 
Humanity 
Index 


265 

275 


















ILLUSTRATIONS 


FACING 

PAGE 

Fig. 1. Unlike bodies attract each other ....... 12 

Fig. 2. Like bodies repel each other.13 

Fig. 3. Simple electrical circuit. 15 

Fig. 4. Illustration of resistance by partially closed valve. 

P, pump. V, valve. E, resistance in electrical 

circuit. 19 

Fig. 5. Simple wet or gravity cell.27 

Fig. 6. Lead cell storage battery.33 

Fig. 7. Edison cell storage battery.37 

Fig. 8. Storage battery charging circuit.40 

Fig. 9. Magnetic field of a solenoid.46 

Fig. 10. Magnetic field of bar magnet as shown by iron 

filings.47 

Fig. 11. Eight hand rule for determining direction of cur¬ 
rent and magnetic lines of forces .... 49 

Fig. 12. Illustrating an induced current. Current started 

in A induces current in B.52 

Fig. 13. Showing a cycle of alternating current .... 55 

Fig. 14. Simple spark discharge circuit.... 66 

Fig. 15. Closed core transformer.68 

Fig. 16. Plain spark gap.71 

Fig. 17. Quenched spark gap.74 

Fig. 18. Non-synchronous spark gap.76 

Fig. 19. Oscillation transformer. The secondary moves up 

and down the rod, inside the primary ... 84 

Fig. 20. Inductively-coupled transmitting circuit ... 86 

Fig. 21. Complete standard inductively-coupled set, in¬ 
stalled on shipboard. 64 

Fig. 22. Circuit diagram impulse transmitter. P S, trans¬ 
former. C, condenser. Q, quenched gaps. L 
and L 2 , primary and secondary oscillation 
transformer. C 2 , short wave condenser. L 3 , 
antenna loading inductance. A, ammeter . . 99 

Fig. 23. Complete installation, impulse type transmitter . 98 

Fig. 24. Complete arc installation on shipboard . Frontispiece 

Fig. 25. Typical crystal detector.Ill 

Fig. 26. Typical receiving condenser with air dielectric 

(insulation).115 


















ILLUSTRATIONS 


FACING 

PAGE 


Fig. 27. Simplest form of receiving apparatus .... 117 

Fig. 28. Simplest form of tuned receiving apparatus . . 118 

Fig. 29. Simple coupled receiving set .... . . 119 

Fig. 30. Direct coupled receiving set.120 

Fig. 31. Inductively coupled receiving circuit . . . . 121 

Fig. 32. Receiving circuit for both long and short waves, 
showing loading inductance and short wave 
condenser. ... 123 


Fig. 33. Inductively coupled set with buzzer testing circuit 125 
Fig. 34. Front view, standard commercial receiver . . . 109 
Fig. 35. Rear view of standard receiving apparatus . . . 127 
Fig. 36. Connections for using vacuum tubes as a single 

detector.138 

Fig. 37. Vacuum tube as detector of undamped waves. Con¬ 
denser in grid circuit.140 

Fig. 38. Reception with grid condenser in circuit. (1) In¬ 
coming oscillations, (2) grid current, (3) grid 
potential, (4) plate current, (5) current in 


phones.141 

Fig. 39. Vacuum tube as an amplifier.143 

Fig. 40. Variations of plate current with grid voltage . . 144 

Fig. 41. Use of vacuum tubes as a regenerative amplifier 

(feed back circuit).146 

Fig. 42. Circuit for use of vacuum tube for reception of 

undamped waves.147 

Fig. 43. Voice modulations of antenna oscillations. A, fluc¬ 
tuations in grid voltage. B, varying amplitude 

of oscillations.151 

Fig. 44. Circuit for vacuum tubes as a generator of un¬ 
damped waves.152 

Fig. 45. Control of antenna current in radio telephony by 

vacuum tube modulator.153 

Fig. 46. Typical antennae.160 

Fig. 47. Assembled two circuit receiving set with crystal 

detector .212 

Fig. 48. Wiring diagram and details of two circuit receiv¬ 
ing set with crystal detector.213 














PREFACE 


Within the past half year the radio art has re¬ 
ceived phenomenal attention from the general pub¬ 
lic. People who hitherto gave it but passing at¬ 
tention have become enthusiastic experimenters 
and have made it their exclusive hobby. 

There are numerous excellent text books pub¬ 
lished dealing exhaustively with radio engineer¬ 
ing in all its many ramifications, but these works 
excellent though they be, are more or less techni¬ 
cal in their make-up. 

Among the many newcomers into the ranks of 
experimenters are people who have neither the 
technical knowledge nor the time to acquire it, and 
who desire a manual as free from technicalities 
as possible, in order to obtain a working idea of 
radio. To meet the demand of that class of reader, 
the author offers this manual. He hopes at least, 
that it will prepare the reader for a better under¬ 
standing of radio, which can be supplemented 
later by perusing more comprehensive works 
already published upon the subject. 

The writer wishes to express his sincere thanks 

and appreciation to Messrs. C. B. Cooper, W. J. 

• • 

Vll 


f 


Vlll 


PEEFACE 


Eoche and J. B. Ferguson of the Shipowners 
Eadio Service for their assistance and advice. 
Also, to Mr. Philip Farnsworth, Counsellor-at- 
law, for the loan of valuable reference works. 

He acknowledges his indebtedness to the various 
publications of the Signal Corps, the U. S. Navy, 
and the Bureau of Standards, for exact data upon 
many subjects. 


John E. Irwin. 


BRIEF HISTORY OF 

RADIO 

CHAPTER I 

EARLY DAYS OF RADIO 

It is appropriate that any explanation of radio 
to the uninitiated should include, however brief, 
something of the origin of the art. 

The complete history would require several vol¬ 
umes and would include the efforts of experi¬ 
menters who have contributed to the final result, 
but who did not in their day even dream of what 
they had individually assisted in constructing. 

The radio art owes its origin to Professor Hein¬ 
rich Hertz, a German scientist, who in the eighties 
conducted a series of experiments which led to 
the construction of the first apparatus for propa¬ 
gating and detecting ether waves, which he de¬ 
scribed in 1888 in his book “ Electric Waves / 9 
Professor Hertz ’s work, however, was not fully 
proclaimed until Guglielmo (William) Marconi, 
then a very youthful Italian student, conceived its 

1 


2 


BADIO 


commercial advantages and ntilizing Hertz’s ex¬ 
periments and his own ideas originated the first 
practical radio stations. 

Hertz, the pioneer, had understood and applied 
the principle of resonance. Marconi took the 
Hertz oscillator and resonator and adapted them 
for a transmitter and a receiver, respectively, by 
making both circuits open instead of closed, and 
grounding the antenna. Tuning between the 
transmitting and receiving antennae in this pioneer 
work was accomplished by increasing or decreas¬ 
ing the capacity of the plates on top of his aerials. 

In his experiments Hertz had used for a de¬ 
tector a microscopic spark gap. Marconi in his 
work utilized a Branley-Lodge coherer as a de¬ 
tector. 

Using the Morse telegraph code, Marconi com¬ 
menced by signaling a few hundred yards, but with 
the aid of the Italian and British governments he 
increased the range of his apparatus until he had 
demonstrated that radio was a practical commer¬ 
cial possibility with unlimited scope. 

It is interesting at this stage to note that Signor 
Marconi, more fortunate than some famous in¬ 
ventors, surrounded himself with associates who 
had the foresight and imagination to picture the 
future possibilities of the new science. It was this 


EARLY DAYS OF RADIO 


3 


that has enabled Marconi to-day, in the prime of 
his life, to reap the material benefits of his pioneer 
work. 

No historical reference to modern radio wonld 
be complete without appreciating the experi¬ 
ments of Sir Oliver Lodge, the famous English 
scientist who, as early as 1888, experimented along 
the lines originated by Hertz and contributed valu¬ 
able aid towards making the art the success of to¬ 
day. Later Professor Lodge was to become asso¬ 
ciated with the Marconi interests, as also was 
another eminent Englishman, Professor J. A. 
Fleming, who has contributed to the radio art 
several valuable text books. In fact, it might be 
stated that he was first to write any substantial 
work on the subject. Later he was to revolutionize 
radio with his original work on vacuum tubes, 
which we will deal with in its place or chronolog¬ 
ical order. 

Following Marconi ’s entrance into the field and 
the filing of his first patent in 1895, radio teleg¬ 
raphy was taken from the academic to the com¬ 
mercial stage and from that date various improve¬ 
ments by innumerable experimenters have fol¬ 
lowed with endless repetition. 

It may be stated, at this stage, without fear of 
contradiction, that radio telegraphy and telephony 


4 


RADIO 


has been productive of more patents and more 
patent litigation than any other science, art or 
industry invented by man. Patents issued to date 
in the United States and foreign countries already 
number tens of thousands. Litigation upon the 
subject has littered the courts. Reference to all 
who have contributed to the art can, therefore, not 
be made within the scope of this volume, and any 
neglect to give credit, where credit is due, is not 
premeditated. We will endeavor to give the 
reader only the principal events which seem to 
occur, as it were, as stepping stones in radio 
engineering. 

Following Marconi’s commercialism of radio, 
as we may term it, came rapid developments on 
both sides of the Atlantic. 

Nicolas Tesla, in 1897, introduced the tuned 
transmitter and receiver, or what was to become 
known as the two circuit transmitter and receiver, 
which was eventually to lead to much litigation in 
the courts. In 1898 Marconi patented his first 
double circuit receiver, retaining, however, his 
original plain aerial transmitter. Della Riccia, in 
the same year, adopted a closed and open oscilla¬ 
tory transmitter, while Braun and Stone, in 1899, 
both devised inductively coupled apparatus. 

Ducretet and Pupin, in 1899-1900, it would seem, 


EAELY DAYS OF EADIO 


5 


were the first engineers to resort to what is known 
as conductively conpled circuits, which were used 
most successfully commercially for a number of 
years prior to the introduction of radio laws and 
regulations. After the promulgation of these 
laws, conductively coupled circuits became imprac¬ 
tical as the wave emitted did not comply with the 
requirements of the new regulations. 

In 1900 Signor Marconi and Professor Braun 
shared the Nobel prize for their efforts in the 
radio field. This was the first public recognition 
of the new science and an acknowledgement of its 
importance in the scheme of human events. 

High Sparh Frequency .—Wireless teleg¬ 
raphy had now reached a stage when its study at¬ 
tracted the brightest minds of the scientifically 
thinking world. 

All the earlier equipments had employed as a 
primary source of energy induction coils, with 
various means of breaking the direct current. 
Owing to mechanical difficulties these 4 ‘ make and 
break” devices were necessarily slow in action, 
with the resultant low spark frequency. The 
manipulation of these early equipments required 
considerable skill on the part of the pioneer opera¬ 
tors to maintain a “spark,” indeed, the old time 
radio telegrapher, in despatching a batch of busi- 



6 


RADIO 


ness, necessarily would conduct a series of experi¬ 
ments during his efforts. 

These induction coil sets gradually gave way to 
“power” sets, in other words, alternating current 
supplied by motor generators, supplied the power 
source. The usual commercial frequency of sixty 
cyles was first employed. While the practical 
operation of radio apparatus was immeasurably 
improved, the low spark frequency objection still 
remained. 

Fessenden appears to be the first radio engineer 
to suggest a remedy to low spark frequencies and 
apparatus known by his name appeared which 
gave forth a high musical note and did much to 
overcome “static” or “atmospherics,” which has 
been and continues to be the bugbear or hoodoo 
of radio. 

A German system known as “Telefunken” also 
utilized a high frequency alternator to produce 
the high musical note. 

These high spark frequency equipments utilized 
either rotating gaps to convert sixty cycle alter¬ 
nations or “quenched” gaps. The latter are used 
almost exclusively in modern equipments, owing 
to their efficiency in their “dampening” effects. 

Perhaps we should here remind the reader, that 
a full or comprehensive study of the above men- 


7 


EARLY DAYS OF RADIO 

tioned apparatus will be found in the portion of 
this work devoted to practical radio, and no effort 
is made in this chapter to an explanation of 
their construction or functioning. 

While the development of radio was progressing 
rapidly, during the decade of 1900-1910, the 
“spark ’ 9 was practically the only system used in 
commercial wireless telegraphy. Great progress, 
however, had been made in what is to-day known 
as the “continuous wave” or the “arc” systems. 
As the former term indicates, this system em¬ 
ployed a continuous or “undamped” wave as its 
principle. 

Poulsen was the originator of the “arc” method, 
while Alexandersen produced a high frequency 
alternator, which, while having a comparatively 
low rate of R. P. M., delivered an exceedingly high 
frequency. Both systems are used extensively to¬ 
day by operating companies. 

An evolution of the vacuum tube, dealt with 
later, also produced another form of continuous 
wave radio transmission, which can be said to have 
put radio telephony where it is to-day. 

Undoubtedly, owing to its greater efficiency, 
continuous wave radiotelegraphy will eventually 
displace the spark systems, although, especially 
on shipboard, both systems are often used in one 


8 


RADIO 


station. This, however, is merely as a convenience 
and a necessity under existing conditions, as a 
complete change from one system to the other 
would be too radical from a commercial or prac¬ 
tical point of view. It is one that will come very 
gradually. 

It will now be necessary to go back to the com¬ 
parative early days of radio to bring the reader 
to the development in the science, which possibly, 
has resulted in the astonishing, and we might say, 
miraculous results that are obtained to-day. 

Vacuum Tube Discovered .—Professor 
J. A. Fleming, after associating himself with 
Marconi, developed what is known as the “Flem¬ 
ing Valve.” This invention was to be the most 
important development in the radio field. 

The Fleming valve was inspired from the ef¬ 
fects of the Edison incandescent electric lamp, and 
takes us into a study of the “electron theory .’ 9 
Thomas Edison, the inventor of the lamp, had 
experimented in its pioneer days and discovered 
that by placing a plate within a bulb separate and 
untouching the filament, a flow of electrons was 
observed from the filament to the plate. 

Fleming, casting about for an improved de¬ 
tector, studied this effect and discovered that this 
flow of electrons was always in the same direction 


EAELY DAYS OF RADIO 


9 


and of a negative nature, flowing from the heated 
filament to the cold plate. This flow could be con¬ 
trolled by inserting a rheostat in the filament cir¬ 
cuit and increasing or decreasing the filament 
current. These valves when properly constructed 
made excellent detectors for “spark ’* radio sig¬ 
nals. 

After Fleming’s valve came the discovery by 
Dr. Lee Deforrest, of the “three element” vacuum 
tube, which he called an “audion.” Deforrest in¬ 
serted what he termed a “grid” between the fila¬ 
ment and plate. This was possibly the most im¬ 
portant discovery yet made in the new science of 
radio, and during the years of the World War, 
was to revolutionize the art. With the coming of 
the audion, methods of amplifying or increasing 
the intensity of radio signals were devised. 

One method of amplification, discovered by 
Armstrong, then a Columbia University student, 
was the “feed-back” or “regenerative” circuit, 
which is now almost universally used in radio 
practice. 

A full description of vacuum tubes and asso¬ 
ciated circuits is not intended here, but will be 
found under that caption in the practical course 
which follows. 


10 


RADIO 


Standard graphical Symbols 


Alternator 
A mmefcr- 
Antenna - 
Arc - — 

C>atTcry - 



or—(ru) 




Variable Inductor 

Key- - --- - -■ ■» 

Resistor. 


-J 


Variable resistor 


—wvw yv- 


1«,«]l!— 

Du7)jer —-__ 

Condenser._ -Hh r ‘ - 

Variable Condenser.— 
Connection of wires— 

KJo connect ion . 

Coof=>1«<d Coils__ 

Variable c©ubb n &-. 

Defector*.._ 

Galvanometer-- -— 

Gab< £>Iain- - m ©__ 

Gab- quenched-- jjjjjjjjj— 

Cj round _ ______ - =i— • 





Switch 5 P 5 T_ 

- -SPOT _ 

. D P 5.T_' 

D.PD.T ..... 

«• rtversing, .,_ 

TeIeb^ on « reeeiver,1J < for (5^) 

Telephone transmitter_ 

Thermoelement- — 

Transformer__ 



or. 


Vacuum tube — — 


Voltmeter. 



Ind O c to r- 


v 






























CHAPTER II 


ELEMENTARY ELECTRICITY 

There is a wonderful phenomena, the exact 
nature of which we know nothing definite, yet we 
are able to govern, actually measure and otherwise 
control its action. This peculiar phenomena is 
called “ electricity . 9 9 In its action we often com¬ 
pare it with water, as it has analogous character¬ 
istics, which are frequently used for comparative 
purposes in teaching the elementary principles of 
radio or electricity. 

It should, however, be carefully borne in mind 
whenever electricity and water are likened to each 
other that expressions of a flow” and “current” 
and other similar terms are merely analogous. 
They are methods that originated in the early days 
of electricity, when electricity was considered 
some form of invisible fluid which actually flowed. 
These terms and expressions are utilized to-day in 
explanatory prefaces only as they are useful in 
forming mental photographs of the theoretical 
action of electricity in motion. 

Electrical phenomena may be placed in two 

11 


12 


EADIO 


general classes, one of which is termed “static’’ 
electricity, when the electrical charges are at rest, 
and the other is 4 ‘dynamic’’ or “current’’ elec¬ 
tricity, when the charges are in motion along a 
conductor. 

When an insulator, such as sealing wax, is 
rubbed with fur, or a glass tube with silk, it ac- 



Fig. 1. Unlike bodies attract each other. 


quires the property of attracting light bodies near 
it, and is said to be c 1 charged.’ 1 This action shows 
that forces exist in adjacent space, and there is 
said to be an “ electrostatic/* or, to use another 
term, a * ‘ static field of force, ’ ’ about the charged 
body. Wlien two charged bodies are brought near 
together they may either be attracted or repelled, 
depending on the nature of the two charges. If the 
rubbed glass is brought near particles touched and 













ELEMENTARY ELECTRICITY 13 

charged by the rubbed sealing wax, they will be 
attracted to it, and similarly, if the rubbed wax 
is brought near particles charged by the glass, 
they will be attracted (Fig. 1); but two bodies both 
of which have been charged by either the glass or 
the wax, will repel each other. Hence, like charges 




Fig. 2. Like bodies repel each other. 

repel each other and unlike charges attract each 
other (Fig. 2). The names “positive” and “nega¬ 
tive” have been given respectively to these 
charges. 

It is common knowledge that a battery or 
dynamo supplies what is known as a current of 
electricity. To obtain the current there must be a 
complete closed or conducting path from the bat- 









14 


RADIO 


tery or dynamo through the apparatus it is de¬ 
sired to be actuated by the current, and back again 
to the battery or dynamo. For example, when 
connecting up an electric bell, a wire is carried 
from one binding post or terminal of the battery, 
to one of the bell, and a second wire is brought 
from the other binding post of the bell back to the 
remaining terminal of the battery. Any break 
in the wire immediately causes the current to stop 
and the bell would cease ringing. This example 
furnishes an illustration of the easy control of an 
electric circuit, since it is only necessary to break 
the circuit at one point to stop the flow of cur¬ 
rent, or to connect across the gap a piece of metal 
to start the current going again. 

Similar considerations apply when we are using 
the common house lighting facilities. Wires are 
brought direct or indirectly, but always in a cir¬ 
cuit, from the electric light plant or station to 
the lamp, a small gap in the socket is provided. 
When the current is on and the circuit complete 
this gap is bridged by a metal connection, this is 
usually controlled by a snap spring. When the 
light is no longer required, you snap the switch 
and the metal connection is opened, the gap is 
formed in the circuit and the current ceases 
(Fig. 3). 


ELEMENTARY ELECTRICITY 


15 


Sometimes the lamps suddenly go out, and it 
is explained that a fuse has been blown. A short 
piece of easily fused metal through which current 
has been passed has suddenly melted. This has 
caused a gap in the circuit and the current ceases to 



Fig. 3. Simple electrical circuit. 


flow and your lights are extinguished. Electricity 
must therefore flow in very part of the circuit 
served, so that it is leaving one side of the battery 
or dynamo and returning to it at the other side. 
The current flowing in a circuit is no stronger at 
one point of the circuit than at another. This is 
proved by connecting a measuring instrument 
called an “ammeter’’ into the circuit. Place the 
ammeter at different points and it will register the 
same at whatever point the test is made. A useful 









16 


RADIO 


illustration of the electric current is a closed pipe 
completely filled with water, provided with a pump 
or some other device for causing a circulation of 
the water. The amount of water which leaves a 
given point in each second is just the same as the 
amount which arrives in the same length of time. 

In the electric circuit we have no material fluid, 
but we suppose that there exists a substance, 
which we call electricity. This electricity behaves 
in the above described circuit in very much the 
same manner as an incompressible fluid in a pipe 
line. We are very sure that electricity is not like 
any material substance that we know, we will, 
therefore, have to imagine current to be a stream 
of electricity flowing around the circuit. 

One way of measuring the rapidity with which 
water is flowing, is to let it pass through a meter 
which registers the total number of gallons which 
pass through. By dividing the quantity by the 
time it has taken to pass, we may obtain the 
rapidity of the flow. There are instruments by 
which it is possible to measure the total quantity 
of electricity which passes in the circuit during a 
certain time. If we divide this quantity by the 
time, we obtain the amount of electricity which has 
passed in one second. This is a measure of the 
current strength. 


ELEMENTARY ELECTRICITY 17 


In practice, however, the strength of the current 
is measured by instruments known as ammeters, 
which show at any moment how strong the cur¬ 
rent is. It also enables us to tell at a glance what 
changes may take place in the current flow from 
moment to moment. We may, also, by means of 
an ampere-hour meter, ascertain the amount of 
energy that has passed over the circuit. These 
two recording instruments, the ammeter and the 
ampere-hour meter, therefore, would correspond 
to the speedometer on an automobile which points 
out, on one dial, the number of miles the car is 
speeding at the moment, and on another dial the 
number of miles the car has traveled. 

Electromotive Force .—Water will not 
flow in a pipe line unless there is some force push¬ 
ing it along, as, for example, a pump, and it cannot 
be kept flowing without continuing the pressure. 
Electricity, also, will not flow in a circuit unless 
there is pressure brought to bear. In the case of 
an electrical circuit a battery or dynamo provides 
this source of pressure, which is called “ electro¬ 
motive force,” or, in other words, a force which 
puts electricity in motion. In common practice 
this is always abbreviated to emf. The larger 
the number of cells in the battery, the greater will 
be the electric pressure and the larger the current 


18 


RADIO 


which may flow in the circuit. The size of the bat¬ 
tery or the dynamo would correspond to the size of 
a tank or reservoir of water, and the amount of 
current which may be allowed to flow in the elec¬ 
tric circuit would represent a pipe in which the 
water from the tank flowed. The amount of water 
in the tank would be expressed in “gallons.’’ In 
the case of electricity the amount of pressure 
would be expressed in “volts” (see definitions), 
and the amount of current would be shown in 
“amperes” (See definitions). 

Resistance and Conductance .—There is 
always some resistance or impediment to a flow or 
current of electricity, just as there is always re¬ 
sistance of some kind which hinders a flow of 
water. In the case of water, some partially closed 
valve or faucet would check the flow, also there is 
always a roughness in the pipe line which causes 
friction. Similarly in*an electric circuit there are 
certain hindrances which are termed by the name 
“resistance.” The greater the resistance the 
smaller the amount of current which will pass 
through the circuit (Fig. 4). 

Resistance is determined by the kinds of mate¬ 
rials of which the circuit is made up, just as the 
passage of a stream of water is determined by the 
character of the path over which it passes, or the 



ELEMENTARY ELECTRICITY 19 

pipe through which it flows. Just as the amount 
of water in a pipe line may be limited by the size 
of a pipe, so may the amount of electricity in a 



valve. P, pump. Y, valve. R, resistance in electrical 
circuit. 

certain circuit be limited by the size and material 
of the wire conducting it. 

In governing the flow of water we use valves 
or faucets to check the flow of water. In handling 
electricity we use ‘‘ resistance coils ’ 1 to govern the 



































20 


RADIO 


flow of current in any given circuit. There is a 
well defined law which is used in this relation, 
which is called Ohm’s law, being named after its 
discoverer, Professor Ohm, and in speaking of a 
given amount of resistance in any given circuit, 
we always describe the circuit as having so many 
ohms resistance, an “ohm” being the unit of 
resistance. 

Certain metals or materials offer more or less 
resistance to a flow of electricity than others. 
These are well known and divided into well defined 
groups. A material through which a current will 
pass readily and with least resistance is called a 
“conductor,” or described as good conducting 
material, while those possessing qualities which 
will oppose great resistance and almost prevent 
any current of electricity to pass are called “insu¬ 
lators” or good insulating material. We also al¬ 
lude to the latter as non-conductors. Among con¬ 
ductors it is well known what amount of resistance 
a piece of wire of a given metal will offer. It is 
from this knowledge that we utilize copper for 
the purpose of conducting electricity without great 
resistance, and why we generally use “German 
silver” to manufacture certain resistance coils 
when we wish to offer resistance in the passage 
of a current. 


ELEMENTARY ELECTRICITY 


21 


It is also known that materials such as glass, 
porcelain and rubber possess excellent insulating 
qualities and are therefore used very largely as 
insulators. However, there is no material that 
will permit the passage of no electricity whatever, 
and for that reason we have what is called “leak¬ 
age current” and “line losses.’’ 

While it is a question of material in determining 
the factor of resistance in a conducting circuit, it 
is also the size of the conductor which must be 
considered. In the case of a given piece of wire 
of a uniform cross section, its resistance is always 
found to be proportional directly to its length and 
inversely to its cross sectional area. 

Electrical resistance in all substances is found 
to depend upon temperature and is found to alter 
more or less with any change of temperature. All 
metals and mostly all alloys used in electrical en¬ 
gineering increase their resistance with a rising 
temperature, while carbons and liquid conductors 
like electrolyte used in batteries, show a decrease 
in resistance as the temperature rises. 

Electrical Control .—Having discussed the 
question of resistance, we should now pass to the 
subject of current control. In radio the need is 
constantly arising for controlling electrical pres¬ 
sure and current to certain required values. This 


22 


RADIO 


is generally accomplished by varying the resist¬ 
ance in the circuit by means of resistors. Resist¬ 
ors are made in a variety of ways and known by 
several names, depending upon their current car^ 
rying capacity and their range. Some are called 
* ‘resistance boxes,’ ’ others, “ rheostats,” and are 
generally manufactured in a form which permits 
of easy variation and are compact for convenience. 
However, banks of incandescent lamps are very 
often used as resistance units and are, indeed, 
most satisfactory in experimental work where fine 
adjustment is needed. The change in resistance in 
such a rheostat is made by switching individual 
lamps on or off as desired. 

Conductors .—Conductors of electricity used 
in leading a current from one point to another are, 
as pointed out earlier, usually made of metals or 
metallic alloys. If the conductor is transmitting 
energy to a distant point, some of that energy will 
be wasted in heat. These losses should be kept 
as small as possible and therefore great care is 
taken in choosing the material and the size of the 
wire. For economic reasons it is desirable that 
the cross section be not too great, and a desirable 
material must be selected that will accomplish two 
purposes, economy and efficiency. After much 
experiment, copper is found to be such a material. 


ELEMENTARY ELECTRICITY 


23 


Where light weight is important and increased 
dimensions not undesirable, aluminum is some¬ 
times used. Steel or iron are seldom used in radio 
work as a conductor. For conductors in antennae, 
where strength and atmospheric conditions must 
be considered, phospher-bronze and silicon-bronze 
are almost exclusively used. Copper, however, is 
the best metal conductor, where all considerations 
must be averaged. 

Now, on the other hand, where resistors or re¬ 
sistance coils are essential, the opposite of good 
conductivity is desired and a material of great 
resistivity is demanded. A metal is required high 
and constant in resistivity, yet not bulky. Iron is 
neither high enough in resistivity nor constant in 
action. German silver or manganese are generally 
acceptable as resistors and found to cause less 
variations in temperature, in fact, their tempera¬ 
ture coefficient in the circuit is practically neg¬ 
ligible. 

Insulators — Non-Conductors. — We 

have dwelt upon the subject of good conductivity 
and must next show the importance of good in¬ 
sulation in the scheme of radio. 

In order that the electric energy may be con¬ 
fined to the definite and limited path that we desire 
in radio, it is most essential that the insulation 


24 


RADIO 


we use be of the best material. Insulators are also 
known as dielectrics, and the latter expression will 
often be used later when we deal with the subject 
of condensers. 

We are all familiar with the fact that electric 
wires are covered with materials composed of lay¬ 
ers of cotton, silk, rubber and compounds of vari¬ 
ous kinds, known to be non-conducting, and that 
they are generally supported on or strung along 
glass, hard rubber, porcelain or compound knobs. 
An excellent compound insulator is one, now 
standard in the Navy, called “electrose.” 

Most insulators employed in radio show a de¬ 
crease in their power of resistance with changes 
of temperature and atmospheric conditions. 
Humidity and fog lower their insulating standards, 
and in the event that such substances as slate, 
marble, bakelite, hard fiber and similar materials 
are used as panel boards, unless they are carefully 
protected from atmospheric conditions will 
“sweat’’ and cause a surface leakage. 

Sources of Electricity .—In preceding 
pages we have alluded to electro-motive force, or 
emf., and having discussed how electrical energy 
can be conducted along definite lines or paths, we 
will go into the question of its source. 

There are several methods in which electrical 


ELEMENTARY ELECTRICITY 


25 


energy may be derived from other sources of 
power. Each one of these power or energy trans¬ 
formations sets up a condition which causes cur¬ 
rent or emf. to flow, in short, produces electro¬ 
motive force. 

The two most common and practical methods 
will be discussed in the following pages. These 
are “static” or “frictional” electricity and “bat¬ 
teries” or electricity produced by “chemical 
action. ’ 9 

In earlier paragraphs we described how a piece 
of sealing wax when rubbed with a piece of fur, 
acquired new properties and could be said to be 
“electrified.” A force would be required to sep¬ 
arate the wax and fur and therefore work is done 
if they are to be moved apart. After rubbing 
the wax and fur both bodies would now have the 
power of attracting light substances, such as 
pieces of tissue paper or light particles of wheat 
chaff. The wax is said to have a negative charge, 
and the fur a positive charge of electricity. 

These charges exist in equal amounts and taken 
together neutralize each other. A body that is 
uncharged is said to be neutral. When these 
charges are at rest on conducting bodies they are 
called electrostatic charges. 

Electrostatic charges, as a rule are very small 


26 


RADIO 


There are, in radio practice, two methods of 
deriving the primary source of power. These are 
from batteries and from “induced” electromotive 
force. We shall deal with each in its turn. 

Batteries .—In general practice, there are 
two types of batteries used in radio work, one 
called a “primary” and the other a “secondary” 
or “storage battery.” 

With a primary cell new energy can be obtained 
by putting in new chemicals or parts, in the sec¬ 
ondary cell, energy is renewed by sending a cur¬ 
rent of electricity derived from a mechanical or 
some other source, through the chemicals already 
in the cell, and by charging and recharging can 
be used over and over again. We shall first de¬ 
scribe the primary battery. 

Wet or Gravity Cell .—If two metal plates, 
one of pure zinc and one of pure copper, not in con¬ 
tact with each other, are immersed in dilute sul¬ 
phuric acid, no chemical action will take place. 
However, when the plates are connected by a wire 
or some other conductor outside of the liquid, a 
current will flow in the conductor, as a chemical 
action takes place in the cell. The sulphuric acid 
acting on the zinc plate forms zinc sulphate, and 
the hydrogen liberated from the acid appears at 
the copper plate. The direction of this flow of 


ELEMENTARY ELECTRICITY 


27 


current is always from the copper plate, through 
the conductor or metallic circuit to the zinc plate 
and back through the diluted acid to the copper 
plate. The copper plate is termed the ‘ ‘ positive ’ 9 
pole and the zinc plate the “negative” pole, and 
the direction of flow is arbitrarily said to be from 
positive to negative. For purposes of simplicity 



Fig. 5. Simple wet or gravity cell. 

in marking terminals or preparing diagrams, the 
plus ( + ) sign is always given to the positive and 
the negative sign (—) to the negative plates 
(Fig. 5). 





































28 


RADIO 


The current given by the simple cell described 
does not remain constant, as it begins to weaken 
after the connection between the plates is made, 
or, in other words, the circuit closed. This dimin¬ 
ishing current is caused by the hydrogen, lib¬ 
erated from the acid, accumulating in small bub¬ 
bles on the copper plate. This accumulation of 
hydrogen bubbles diminishes the area of contact 
of the liquid on the faces of the copper plate, thus 
increasing the resistance of the cell. This action 
is called < ‘ polarization.’ 9 To overcome this, what 
is known as a 1 ‘depolarizer’’ is utilized, in the 
form of a chemical substance added to the acid, or 
electrolyte, as the sulphuric solution is also called. 
The action of the depolarizer is confined to the 
positive plate and is kept from contact with the 
negative plate. 

There are two principal types of primary cells, 
the i ‘ wet ’ 9 and ‘ ‘ dry ’ 9 cells. The wet or ‘‘ gravity 9 9 
cell, above described, is used largely by telegraph 
and telephone companies, due to economy and also 
as it is mainly free from polarization. If a large 
output is desired, the internal resistance must be 
low, that is, with a minimum of polarization. In 
these cells the depolarizer is generally placed in 
the bottom of the cell and is kept free from the 
electrolyte by gravity, hence the name. The cop- 


ELEMENTARY ELECTRICITY 29 

per electrode is placed in this solution which con¬ 
sists of copper sulphate. The zinc negative plate 
is kept separate in the sulphuric electrolyte above. 

The voltage given by the average cell is between 
one and two volts per cell. The voltage of a cell 
depends upon the substances used for plates or 
electrodes, and is also effected by the electrolytic 
solution. Therefore, many varieties of electro¬ 
lytes are used when the electrodes are copper and 
zinc, but all give approximately one volt per cell. 

When a certain electromotive force is required 
and no regular source of supply available, it is 
useful to know that an emergency source of volt¬ 
age may be obtained by taking two different kinds 
of metal and placing them in any kind of acid, or 
even in water. It must be remembered, however, 
that the solution attacking the plates most vio¬ 
lently will produce the best results, bearing in 
mind the above remarks regarding polarization. 

Dry Cells .—The dry or sal ammoniac cell is 
used largely in radio, not for its superior qualities 
as compared with the gravity cell, but because of 
its convenient, compact form. The solution of sal 
ammoniac used in it is contained in an absorbent 
material and the cell is thoroughly sealed against 
spilling or leakage. The outer shell is made of 
zinc, forming one electrode. The positive elec-* 


30 


RADIO 


trode is a carbon rod in the center, this is sur¬ 
rounded by a mixture of carbon and manganese 
dioxide. The latter mixture is saturated with a 
sal ammoniac solution and takes up most of the 
interior of the container. This sal ammoniac 
electrolyte is partly in a depolarizing mixture and 
partly in a porous separator placed between the 
zinc and depolarizing mixture. 

These dry cells are not as free from polarizing 
effects as the previously described wet or gravity 
cells. They are made in several sizes. For heavy 
or ignition purposes they will deliver a current of 
thirty amperes when short-circuited, provided 
they are new or little used. They lose their energy- 
producing powers very quickly when used con¬ 
stantly, but in intermittent service have a fairly 
useful term of life, sometimes six months. 

Dry batteries for telephones and bells are gen¬ 
erally made smaller, delivering about twenty 
amperes upon short-circuiting, but lasting longer 
than ignition cells, sometimes they are useful for 
over a year. 

Miniature dry cells for vacuum tube work and 
for flashlights, are made in varying sizes, but lose 
their effectiveness quickly, of course, depending 
upon the period the vacuum tube or flashlight is 
used. 


ELEMENTARY ELECTRICITY 31 

The emf. developed in an unused dry cell is 
from 1.5 to 1.65 volts. In purchasing new cells 
the reader should know that any new dry cell hav¬ 
ing a less emf. than 1.4 volts indicates a defect 
or deterioration through long “shelf life.” 

The amount of energy delivered from the dry 
cell increases with increasing temperatures, but 
the higher the temperature, the faster does the cell 
deteriorate when not in use. It is therefore best 
to keep them in a temperature below 25 degrees 
centigrade. 

Owing to various causes, due to compactness in 
manufacturing and its comparatively rapid polar¬ 
ization, dry cells are not useful for delivering a 
steady current for a long time in service and 
should only be used in radio when an intermittent 
current or a very small current is required, such 
as plate battery service or buzzer ringing. When 
heavier duty is required, it is much more prefer¬ 
able and economical to utilize “storage” or sec¬ 
ondary batteries, described below. 

Storage or Secondary Batteries .—The 
difference between the gravity primary cell, pre¬ 
viously referred to, and the secondary or storage 
cell, is in the method of renewing the active mate¬ 
rial. While the primary cell is renewed by sup¬ 
plying new electrolyte and replacing the worn out 


32 


RADIO 


zinc electrode with a new one, dry cells cannot be 
renewed. In the storage battery, however, the 
necessary chemical conditions of the plates is re¬ 
stored by the action of a current of electricity from 
some outer source, usually from a dynamo. 

While the cell is supplying emf., it is said to 
be ‘ 1 discharging ’ 9 and when receiving a renewal 
of energy it is said to be “charging.” The direc¬ 
tion of the current when charging is always op¬ 
posite to the current when discharging. 

Storage batteries in general have low internal 
resistances when in good order and will therefore 
deliver relatively large currents, this is a great 
advantage. Care must, however, be taken to pre¬ 
vent accidental short-circuiting, as this would 
cause an excessive current and rapid deteriora¬ 
tion, or even ruination, of the battery. 

Voltage changes during the period of discharge 
are small and thus fairly-constant current can be 
maintained. 

There are two types of storage batteries in gen¬ 
eral use, the “lead” cell and the “Edison” or 
“alkaline” cell. 

The Lead Plate Cell .—In the cell type of 
battery, the plates are made of lead, in the form of 
a grid. Each plate contains many tiny cells, like 
honeycomb, and often called by the name “grid.” 


ELEMENTARY ELECTRICITY 


33 


Alternate jjoaitiv* 
end rvsW>tve lead 
PUfet 


es 



Filler Ca>fc> 

Di'rvdin^ Fbsts 
Wisher 1 

Celle)oid (^ Antaingr 
Level of L lectrolyta 


Alternade |=>l«k'H 

An 3 T 

■5efiara,Tor-s 


«« 


Fig. 6. Lead cell storage battery. 


Into these noneycombed cells is heavily pressed, 
or forced, a mixture of red lead, litharge and 
sulphuric acid. When two plates thus prepared 
are immersed in an electrolyte consisting of a 
twenty per cent sulphuric acid solution, and an 
electric current passes between them, hydrogen 
will accumulate on the plate from which the cur¬ 
rent leaves the cell, thus in one plate the active 































































34 


RADIO 


material is reduced to a spongy lead, and in the 
other the same material is being changed to lead 
peroxide, as it takes up oxygen. The cell now con¬ 
tains a lead peroxide plate, called positive ( + ) 
and a spongy lead plate, called negative (—) 
(Fig. 6). 

After the charge is cut off, assuming it is fully 
charged, if the cell is connected in a circuit, cur¬ 
rent will flow in an opposite direction to that by 
which it was charged. The cell upon completion 
of the full charge, should show a voltage, on open 
circuit, of approximately 2.2 volts, this, however, 
will quickly drop to about 2 volts. As the battery 
is discharged the voltage will gradually fall. The 
discharge should never be carried below 1.75 volts. 

The container of a lead cell must be of a mate¬ 
rial sulphuric acid will not attack and is usually of 
either glass or hard rubber. The former for large 
stationary batteries and the latter for the portable 
types. 

The negative plates appear gray and the posi¬ 
tive reddish in color. 

There are innumerable types and each manu¬ 
facturer carefully enumerates on the name plate 
the specific rate, in amperes, of charge and dis¬ 
charge. This is necessary as he is the only one 
who knows the size, weight and number of plates 


ELEMENTARY ELECTRICITY 


35 


in the cell, upon which the discharge and charg¬ 
ing rate is based, and the life and general efficiency 
of the battery is greatly decreased if this normal 
rate is not adhered to. 

There is a chemical action between the lead and 
the electrolyte, which forms lead sulphate during 
the course of a discharge. This uses up the acid 
and the density of the electrolyte grows less, this 
results in the formation of lead sulphate, whitish 
gray in appearance (when dry) which is dissolved 
in the solution. 

For testing the density of battery electrolytes, 
an instrument called a ‘‘hydrometer’’ is the best 
instrument to use, as the density of the solution 
is the best indication of its condition. In other 
words, the density of electrolyte rises and falls 
with the charging and discharging of the cell, and 
a test of the density or specific gravity of the solu¬ 
tion readily indicates its condition. 

Great care is required in the handling of stor¬ 
age batteries to prevent ‘ ‘ sulphating. ’’ 

If a cell is repeatedly charged and discharged 
at its normal rate, as indicated by the manufactur¬ 
er’s name plate, the amount of lead sulphate 
formed will be small and not harmful. However, 
if the battery is misused, for instance, charged 
and discharged at an excessive rate, or perhaps 


36 


RADIO 


\ 

allowed to be idle when in a rundown condition, 
there will form an excessive deposit of lead sul¬ 
phate. As the crystals of sulphate increase they 
crowd out the active materials, stresses are formed 
and the plates disintegrate or buckle. This ren¬ 
ders the cell into such a condition that it is almost 
impossible to repair, and certainly the battery 
will never be normal again. 

Storage batteries of all types, both lead and 
alkaline, are graded when manufactured and rated 
according to the ampere-hour capacity. This 
capacity is generally expressed by the maker on 
the same name plate as the rate of charge or 
discharge. The larger the plate the greater may 
be the current used from it. For example, a forty 
ampere hour battery should yield one ampere for 
forty hours, or, to put it in another way, ten 
amperes for four hours. If, however, five amperes 
is the rate mentioned on the normal discharge and 
charge rate of the cell, it should only be discharged 
at that rate and also recharged at that rate, which 
would give the normal usefulness as five amperes 
for eight hours. 

Batteries are seldom used as they were intended 
and it is thus that so many experimenters have 
considerable trouble and do not enjoy the full life 
of the cell. 


ELEMENTARY ELECTRICITY 37 

Edison Cells .—This is a type of storage bat¬ 
tery developed by the famous Thomas Edison, as 
the name indicates, and also known as the “ Nickel - 
Iron and Alkaline Cell” (Fig. 7). 

In construction, the positive plate consists of 


Valve 


Positive t>ot« 


vJc^h've tx>le 
. .Hard rubber 
^and cap 


-Cell cover 

lie^otive Gri 

Pin insulator 
Side Insulator 


steel Contai 


cell bottom 



Copper wire 
Call cover 
Stuffing b oa . 

Qland n'n^ 

Stuffing box 

Weld to cover 
Sbocin^ washor 
Connecting rod 
Positive ^rid 
<3 rid aeb^nator 
Seamless steel rir ^3 

Fositiva tube^ 


Suspension bow 


Fig. 7. Edison cell storage battery. 


alternate layers of nickel hydrate and pure nickel 
flake, packed in perforated nickel-plated steel 
tubes. Several are arranged in a steel frame. 
The negative plate is of iron oxide packed simi¬ 
larly. These plates are immersed in a twenty 
















































































































38 


EADIO 


per cent solution of caustic potash and water, and 
the whole is contained in a tightly sealed sheet 
steel container. This electrolytic solution carries 
oxygen between the plates, but does not form 
chemical compounds with the .active materials, 
remaining approximately constant in density dur^ 
ing charge and discharge. 

The voltage of an Edison cell while charging 
may rise to 1.8 volts. When discharging this will 
drop suddenly to about 1.4 volts and as the dis¬ 
charge continues will drop more gradually to 1.1 
volts, near the end of the discharge. Discharge 
should not be allowed to go below 0.9 volt; when 
that rate is reached the cell should be recharged. 

If it is found after much use that the density of 
the alkaline electrolyte has fallen as low as, about, 
1.16, measured by the usual means of ascertaining 
specific gravity of liquids, the solution must be 
renewed. This should be done by pouring off the 
old and refilling with entirely new electrolyte. 

The height of the electrolyte above the plates 
should always be kept at about half an inch. This 
applies to both lead and Edison cells. As there is 
always more or less evaporation of the solutions, 
this may be accomplished by adding distilled or 
chemically pure water to bring the height half an 
inch above the plates. 


ELEMENTARY ELECTRICITY 


39 


Comparisons of Storage Batteries .— 

The construction of previously mentioned types 
of secondary batteries is so radically different, 
that a brief comparison of the two is not out of 
place. 

The lead cell will suffer serious injury if not 
well cared for and if not charged and discharged 
according to the use for which it is rated. Fur¬ 
ther, it will deteriorate rapidly if allowed to re¬ 
main idle without care. 

An Edison battery, on the other hand, by nature 
of its sturdier construction and the materials 
utilized, may be said to be as near “fool-proof 99 
as anything thus far placed upon the market. It 
will retain its charge over a long period of idle¬ 
ness. It may remain idle for an indefinite time, 
either charged or discharged, without injury. It 
may be completely short-circuited and totally dis¬ 
charged without harm, whereas this would ruin a 
lead cell. An Edison cell can be charged or dis¬ 
charged at rates differing from its normal 
rate, while it has been previously shown that 
the lead cell must be handled at near its normal 
rate. 

Charging Storage Batteries .—While the 
general method of charging both lead and Edison 
cells is similar, there are features which are 


40 


RADIO 



Fig. 8. Storage battery charging circuit. 












ELEMENTARY ELECTRICITY 


41 


not alike that would require some differentia¬ 
tion in the description of these charging 
methods. 

Lead Cells .—Previously we have mentioned 
that there are certain charge and discharge rates 
prescribed for certain types and sizes of lead cell 
batteries. 

While a battery is receiving a current from some 
outside source it is said to be “charging.” 

In Figure No. 8 is given a diagram of a circuit, 
which is typical for charging batteries. The 
dynamo, or supply of direct current, is marked 
D, and is connected through the ammeter and 
rheostat, marked R, to the battery, so that the 
positive pole of the supply source or dynamo, is 
connected to the positive pole of the battery; this 
will send the charging current against the electro¬ 
motive force of the battery. To thus connect the 
positive pole of the dynamo to the positive pole 
of the battery, is most important, as a reversal of 
this would cause the storage battery to discharge 
instead of charge and cause great injury to the 
cells. 

Before charging, an inspection of the electro¬ 
lyte should be made and if found less than one- 
half inch above the top, chemically pure or dis¬ 
tilled water should be added until that amount of 


42 


RADIO 


electrolyte shows over the top of the plate. Do 
not spill the water over the top of the cover of the 
cell, or a short circuit will result through the 
water from the positive to the negative poles and 
a leakage occur, resulting in a total discharge of 
the cell, if the leakage is allowed to continue. 

If suitable measuring instruments, such as a 
voltmeter and ammeter, are not used, it may not 
always be known which is the positive and nega¬ 
tive line in the source of supply. A very simple 
experiment may determine this question. Take a 
glass of water that contains a little salt or acid, 
place both supply leads in the liquid, being care¬ 
ful to keep them apart, say, by half or one inch. 
Bubbles will be observed to come from the nega¬ 
tive terminal. 

For lead cells, in charging, it is necessary to 
allow two and one-half volts for each cell. If a 
smaller voltage than that which is to be reached 
by the cell, you would discharge instead of charge 
the cell. If the source of supply voltage is not 
sufficient to charge all your cells in series, they 
may be divided into groups and these groups may 
be placed parallel to each other. If this arrange¬ 
ment is necessary, care must be exercised that 
the negative lead from one bank of cells in series, 
to the negative pole of the other bank, and from 


ELEMENTARY ELECTRICITY 


43 


positive to positive terminals of each bank, then 
the leads from the two hanks thus joined will be 
lead as described previously. From the positive 
pole to the positive terminal of the dynamo and 
negative to negative. 

Hydrogen is given off from charging batteries, 
and great care must be taken to keep naked lights 
from the vicinity of the cells, or an explosion will 
result. Some very painful accidents have hap¬ 
pened to numerous unwary people who have, for 
instance, lighted a match to peer into a charging 
battery, in order to ascertain its condition. This 
precaution applies to both lead and Edison cells. 

Edison Hattevy Charging .—The same 
circuit utilized for charging lead cells may be 
employed for charging Edison cells. 

The charging source should have a voltage 
equal to 1.85 times the number of cells in series. 

Before starting to charge, open the covers of 
the compartment, if the battery is in one. See 
that the solution is at the proper level. 

Do not allow the temperature of the solution 
to exceed 115 degrees Fahrenheit. Excessive tem¬ 
perature on charge will shorten the life of the 
battery. 

As in lead cell charging, be sure to connect the 
positive side of the line to the positive pole of the 


44 


RADIO 


battery, and the negative line to the negative pole. 

The specific gravity of the solution will not 
change during the charge or discharge except in 
cases of extreme low or high temperature and 
therefore hydrometer readings are of no value in 
determining the state of charge or discharge of 
the battery. 

The proper length of charge is determined by 
the extent of the previous discharge. If the bat¬ 
tery is totally discharged, recharge it at the nor¬ 
mal rate for the proper number of hours. If the 
battery was only one-half discharged, recharge at 
the normal rate for one-half the time, etc. 

If the extent of the previous discharge is un¬ 
known, charge at the normal rate until the volt¬ 
meter reading has remained constant for thirty 
minutes at about 1.80 volts per cell, with normal 
current flowing. 

If necessary, and full capacity is not required, 
a battery may be taken off charge at any time. 


CHAPTER III 


MAGNETISM AND ELECTRO-MAGNETISM 

There is a form of iron found in the earth 
known as black oxide of iron, also called magne¬ 
tite or magnetic iron ore. This particular iron 
ore has remarkable properties. For instance, if 
a piece of magnetite is dipped into iron or steel 
filings, the filings will adhere to it and is known 
as a “natural magnet.” If a small piece of this 
substance is suspended by a very slender thread, 
such as silk, it will point in northerly and south¬ 
erly direction. 

If a small rod of iron is brought near a piece 
of magnetite, or is rubbed on it in a certain way, 
it will show the same properties as the piece of 
magnetite. If the rod be made of hard steel this 
effect will persist after the magnetite has been 
removed from its vicinity, and is known as a 
“permanent magnet.” 

We are almost all acquainted with the horse¬ 
shoe shaped magnet, and probably have played 
with them when children. 


45 


46 


RADIO 


Magnets are also made by winding a coil of 
wire around a rod of soft iron and passing an 
electric current through the coil (Fig. 9). As 
long as the electricity passes through the coil the 



Fig. 9. Magnetic field of a solenoid. 




iron is magnetized and is called an ‘ ‘electro¬ 
magnet.” These are the familiar examples we 
find in electric bells, buzzers and telegraph 
sounders, and if you screw the ear cap off a tele- 















MAGNETISM 47 

phone receiver you will find an excellent simple 
electro-magnet. If the bar around which the coil 
is wound is made of certain hard steel, that bar 
would be permanently magnetized. 

A small steel rod mounted pivocally will turn 
in almost a north and south direction and is the 
familiar compass needle used by mariners to de¬ 
termine the direction they are proceeding. The 



Fig. 10. Magnetic field of bar magnet as shown by iron 

filings. 


end pointing north is called the “North Pole” 
and that pointing south, the “South Pole.” 

Two magnetic poles are said to be alike when 
they both attract or both repel the same pole. If 
one pole attracts the other they are unlike, if a 
pole repels another, they are alike, therefore, as 
previously explained in the discussion of negative 
and positive connections of a battery, like mag- 







48 


BADIO 


netic poles repel each other and unlike poles at¬ 
tract each other. It is then very easy to deter¬ 
mine which is the north or south pole of a magnet 
by placing a small compass near the magnet and 
observing which way the needle points. 

Place a sheet of paper over a magnet and 
sprinkle iron filings upon it and you will find they 
will arrange themselves in two groups, one group 
over the north and the other over the south pole 
(Fig. 10). This indicates that there are forces 
in the space around the magnet that act on its 
poles. These forces are called “magnetic lines 
of force” and appear to center in the two poles of 
the magnet. 

The space around the magnet in which these 
lines of forces may be detected is called the “mag¬ 
netic field,” and the direction of the magnetic 
field is the direction in which the compass needle 
will point, if a compass is used as above described. 
This needle will always point north. 

Experiments with a compass, as shown above, 
determine that there is a magnetic field about a 
wire in which a current of electricity is flowing, 
and that this field is in the form of concentric cir¬ 
cles about the wire. These circles lie in planes 
at right angles to the axis of the wire. If the 
wire is grasped by the right hand with the thumb 


MAGNETISM 


49 


pointing in the direction of the current, the fingers 
will sliow the direction of the magnetic field (Fig. 
11). This field extends to an indefinite distance 
from the wire, but as it becomes more distant the 
effect becomes correspondingly feeble and there is 



Fig. 11. Right hand rule for determining direction of 
current and magnetic lines of forces. 

greater difficulty in detecting its presence. If 
the current is cut off, the magnetic field likewise 
disappears. When a current is flowing in a wire, 
we must imagine the magnetic field as started and 
sweeping outward from the conductor, with the 
axis of the wire as its center. 

If the wire in which a current is flowing is bent 
into many circles or turns and these turns wound 
close together the intensity of the magnetic field 
is increased in direct proportion to the number 
of turns in the wire. 

If the space within the coil is filled with iron, 






50 


RADIO 


the magnetic lines or ‘ 1 flux” is greatly increased. 
This is due to a peculiar property of iron which 
is called magnetic 4 ‘ permeability. ’ ’ This is to 
say that when the space is filled with iron instead 
of air alone that the magnetism is stronger. 

It should be remembered that this magnetic in¬ 
duction in a coil depends upon the number of 
ampere turns in the coil and the permeability of 
the iron. 

If the current in the windings is reversed the 
direction of the magnetic field is also reversed. 

If two different magnetic fields are brought to¬ 
gether in the same space, with their directions 
parallel, a force is always developed. If the lines 
of magnetic flux are in the same direction, the 
two fields mutually repel one another, and if the 
flux lines are in opposite directions the two fields 
will be drawn together. When a current flows in 
a wire which is at right angles to a magnetic field, 
a force will act on the wire. 

When the wire which carries the current is at 
right angles to the direction of the magnetic field, 
the pushing force on the wire is equal to the 
product of the current, the intensity of the mag¬ 
netic field, and the length of wire which lies in 
the magnetic field. 

If the wire makes some other angle with the 


MAGNETISM 


51 


direction of the magnetic field, the direction of 
the force is still the same as for the right angle 
position, bnt the value of the force is smaller. In 
the single instance that the direction of the cur¬ 
rent coincides with the direction of the magnetic 
field, the force is zero. 

This push on a single wire is in most cases 
small, but by arranging many wires in a very in¬ 
tense magnetic field, very large forces may be 
obtained. The powerful turning effect of an elec¬ 
tric motor depends upon these principles. 

There is always a magnetic field about an elec¬ 
tric current. The lines of magnetic flux are 
closed curves and the electric circuit is also 
closed. The lines of magnetic flux are then 
thought of as always interlinked with the wire 
turns of the circuit. The number of flux lines 
through a coil will depend upon the current, and 
any change in the current will change the num¬ 
ber of linkings. If there are two turns of wire 
the circuit will link twice with the same magnetic 
flux, and so, for any number of turns the number 
of linkings increases with the number of turns. 

Induced Electromotive Force .— 
Whenever there is any change in the number of 
linkings between the magnetic flux lines and the 
wire turns, there is always an emf. induced 


52 


RADIO 


in the circuit. If the circuit is closed a current 
will follow. This is called an induced cur¬ 
rent. As an example we can observe the effects 
produced by two solenoids fixed in the position 



Fig. 12. Illustrating an induced current. Current 
started in A induces current in B. 

shown in Fig. 12. If a current is started in one 
of them, A, there will be a current induced in the 
other, which will continue to flow as long as the 
current in A is increasing. If the current in A 
becomes steady, there is no current induced in B. 
If the current in A falls off, the induced current 
in B is reversed in direction. In all cases it must 












MAGNETISM 


53 


be remembered that the magnetic field about the 
induced current tends to oppose the change that 
is causing the induced current. The magnitude 
of the induced emf. depends upon the time rate 
of change of the number of linkings. 

Inductance .—The value of inductance de¬ 
pends upon the shape and size and upon the 
permeability of the medium about the circuit. 
The inductance does not depend upon the current 
which is flowing, except when iron is present. By 
coiling up a piece of wire in many turns and intro¬ 
ducing it into the circuit, the inductance of the 
circuit may be greatly increased. In that case 
the inductance is said to be concentrated. It must 
not be overlooked that the entire circuit has induct¬ 
ance. This may be distributed more or less uni¬ 
formly throughout the circuit. 

If a piece of wire is connected to one terminal 
of a dry cell, and tapped on the other terminal, a 
very slight spark may be seen in a darkened room. 
If a coil of many turns of wire is included in 
series, with this cell, the same process of tapping 
will show brilliant sparks, particularly if the coil 
has an iron core. The explanation of this lies in 
the fact that the cell voltage of 1.5 is too feeble 
to cause much of a spark. However when the 
large inductance is included in the current, there 


54 


RADIO 


is a large number of linkings between wire turns 
and flux lines. If these flux lines collapse sud¬ 
denly, as they do when the circuit is broken, there 
will be a large change in the number of linkings 
taking place in a very small interval of time. 
This principle is made use of in ignition apparatus 
and spark or induction coils. 

In mechanics it is well known that a piece of 
matter cannot set itself in motion and that energy 
must be supplied from outside. So in the elec¬ 
tric circuit, a current cannot set itself in motion, 
and energy must be supplied by some form of 
generator or source of electromotive force. 

As an illustration of inductance we may use the 
following example. When a nail is forced into a 
piece of wood, the mere weight of the hammer as 
it rests on the head will produce but little effect. 
However, by raising the hammer and letting it 
acquire considerable speed, the kinetic energy 
stored is large and when the motion of dropping 
the hammer is stopped, this energy is expounded 
in forcing the nail into the wood. In the electric 
circuit a cell with its small emf. can only cause 
a feeble spark. By including a piece of wire of 
many turns in the circuit, however, a small cur¬ 
rent will enable a large amount of energy to be 
stored in the magnetic field, if the inductance is 


MAGNETISM 


55 


large. Then when the circuit is broken and the 
field collapses, this large amount of energy is re¬ 
leased suddenly, and a hot spark of considerable 
length is the result. 

Alternating Current • — An alternating 
current is one in which electricity flows around the 
circuit, first in one direction and then in the oppo- 



Fig. 13. Showing a cycle of alternating current. 

site direction, the maximum value of the current 
in one direction being equal to the maximum value 
in the other. All changes of current occur over 
and over again at perfectly regular intervals. A 
graphical representation of this is shown in Fig. 
13, the potential commences at A, which repre¬ 
sents zero potential, rising to its maximum voltage 
of, say, 110 volts, then falling to zero at B, the 
current then reverses itself and flows in the oppo¬ 
site polarity, again rising to 110 volts and drop- 


















56 


KADIO 


ping to zero at C. From A to B represents an 
“alternation” and from A to C, a “cycle,” thus 
each cycle consists of two alternations. 

The frequency of alternating current is deter¬ 
mined by the number of cycles per second. In 
ordinary commercial use, for lighting and power, 
25 to 60 cycles per second is the usual frequency, 
mostly 60 cycle. In Europe they often use 50 
cycle alternators. However, in radio practice 
higher frequencies are desirable and in modern 
spark transmitters 500 cycles is considered the 
standard. This gives the emitted signals a high 
musical tone, as the spark frequency from such 
an alternating current would be 1,000 per second, 
or one spark discharge for every alternation of 
the current. This matter of spark frequency is 
only mentioned in passing and will be fully dis¬ 
cussed later under the caption of radio trans¬ 
mission. 

Alternators .—Alternating current is pro¬ 
duced by electrical machinery. Electrical ma¬ 
chines are used for conversion of power from 
mechanical to electrical form, or vice versa . If 
driven by some sort of prime mover like a steam 
engine, gas engine or water wheel, they convert 
mechanical power into electrical power and are 
called “generators.” If supplied with current 


MAGNETISM 


57 

and used to drive machinery, vehicles, or other de¬ 
vices, thus converting electrical power into me¬ 
chanical power, they are called “motors.” 

While there are various types of motors and 
various types of generators, the difference is more 
in the use than in the appearance or construction. 
Electric machines may he built for either direct 
or alternating current. If a generator of alter¬ 
nating current, called an alternator, is driven by 
a motor, this machine is known as a motor gen¬ 
erator. 

In general, it is a motor generator that is em¬ 
ployed in common radio practice, as a source of 
power. 


CHAPTER IV 


EXPLANATION OF RADIO 

Radio signals are produced by propagating 
waves in that peculiar medium known as the 
ether. These waves are originated by setting up 
high frequency oscillations radiating from an 
“antenna” or, as it is also known, an “aerial.” 

The antenna oscillations cause waves in the 
surrounding ether to be radiated into space in all 
directions at the tremendous speed of 186,000 
miles per second, which is the same speed at 
which light travels. 

These ether waves, coming in contact with an 
antenna at a receiving station, set up in the re¬ 
ceiving antenna oscillations which, by means of 
suitable apparatus (hereafter described in this 
volume), are rectified by means of a detector so 
as to be audible to the human ear, generally by 
the use of telephones. 

By this means the signals of the Morse code or 
telephonic speech can be carried on. 

The force or amplitude of ether waves depends 
on the energy developed in the antenna circuit. 

58 


EXPLANATION OF RADIO 


59 


The greater the amplitude of ether waves, the 
farther do they travel and the farther can they 
be perceived before their force is spent. But the 
amplitude of the waves in no way atfects their 
rate of travel, nor their frequency. 

The speed at which these waves follow each 
other is termed 44 wave frequency.’’ Wave fre¬ 
quency depends upon the characteristics of the 
sending circuit, and is controlled by varying the 
capacity, inductance and resistance. In other 
words, by varying the size of the condenser unit 
or the inductance coil. Details of various types 
of apparatus, such as condensers, etc., are dis¬ 
cussed elsewhere and will be alluded to in these 
preliminary pages only as aids to a general un¬ 
derstanding of radio. 

A given circuit will produce oscillations at only 
a certain fixed rate depending on the factors of 
inductance, etc., just as a pendulum can swing 
at only a fixed rate, depending upon its length 
and weight. In ordinary commercial practice 
the wave frequency varies from as much as 
2,000,000 per second to as little as 100,000 per 
second. 

Wave Length .—We now come to what is 
known as 44 wave length,” or in other words the 
distance from the peak of one wave to the peak of 


60 


RADIO 


the succeeding wave. As an analogy we can pic¬ 
ture the distance from the top of a water wave to 
the top or peak of the succeeding wave, although 
ether waves may be of different form to water 
waves. 

Dividing the velocity of the waves, 186,000 miles 
per second, by the number of waves per second, 
gives us the wave length. We may put this in 
another form and say that the product of the 
wave length by the frequency is always 186,000. 
It will, therefore, be seen that it is of importance 
that a student should bear in mind the speed 
with which ether waves travel. 

In discussing wave lengths, it should be care¬ 
fully noted that it is only by means of variations 
of wave lengths that it is possible to operate a 
number of radio stations within the same area or 
region. Any desired wave length can be obtained 
by varying the circuit which determines wave fre¬ 
quency. 

Wave lengths used in commercial practice vary 
from a few meters to thousands of meters. 

Wave length plays such an important part in 
radio that a perfect understanding of the subject 
is essential. For illustrative purposes, we may 
compare several radio stations working in the 
same locality, on similar wave lengths, to several 


EXPLANATION OF RADIO 


61 


persons speaking in the same room at the same 
time. A listener at a receiving station, or an¬ 
other person listening in the same room to the 
speakers, would be “jammed,” or “interfered 
with,” to use radio terms of expression. 

Supposing you could devise something that 
would eliminate all but one of the stations and all 
but one of the speakers, you would eliminate in¬ 
terference. In radio, interference is overcome by 
what is known as “tuning.’’ Stations in the same 
vicinity, by laws, regulations and mutual agree¬ 
ment, employ different wave lengths. By a re¬ 
ceiving instrument known as a “tuner” or “re¬ 
ceiver” it is possible to listen to only one station, 
or if desired, an arrangement of circuits can be 
made for “broad tuning” and “sharp tuning.” 
As the names imply, broad tuning enables the 
person receiving to listen to several stations, 
working on various wave lengths (within a cer¬ 
tain scope), but with resultant interference, while 
the latter permits only the reception of signals 
from one station. 

In commercial practice this arrangement for 
listening in on broad tuning is very desirable, as 
an operator is enabled to catch any “call,” and 
by arrangement of switches and dials rapidly 
throw over to the tuning devices providing for 


62 


RADIO 


sharp or selective tuning. Details of such re¬ 
ceivers will be found under that heading within 
these covers. 

Wave Trains or Groups .—A “wave 
train’’ is a group of ether waves, sent out at one 
condenser discharge and contains numbers of in¬ 
dividual waves depending on the circuit conditions 
previously alluded to. 

Wherever these waves strike a receiving an¬ 
tenna in their travel from the transmitting sta¬ 
tion, they will set up in the receiving antenna 
oscillations identical to those from the trans¬ 
mitting station. These oscillations, as we have 
shown, are very frequent, usually so rapid (say 
over a million per second) that they are beyond 
the range of the audibility of the human ear which 
can only detect sounds of a frequency not greater 
than 4,000 or 5,000 per second. 

We must therefore utilize some device to detect 
ether waves. In common practice this is called 
a “detector” and using a pair of telephones in 
conjunction therewith we are enabled, as it were, 
to take the energy from the antenna, which, pass¬ 
ing through the detector produces a click in the 
telephones. The characteristics of the many de¬ 
tectors together with their associated receiving 
circuits is fully dealt with in succeeding chapters. 


EXPLANATION OF EADIO 


63 


Resonance .—From the foregoing, it will be 
seen that high frequency oscillations, radiated as 
ether waves from a transmitting antenna, will set 
up characteristic oscillations in a receiving an¬ 
tenna, within their path or range. 

In practice, however, best results are obtained 
only when the sending and receiving antennae are 
“in tune,” or as it is commercially termed, “in 
resonance . 9 9 

To properly understand this phenomena, it 
would be well to take examples well known to 
everybody with even a slight knowledge of music, 
or through acoustics. 

Take the example of two bells of similar tone, 
strike one and the other bell will respond without 
being struck. Also, the instance of two tuning 
forks of the same characteristics, strike one until 
it gives forth a musical note, it will, on the prin¬ 
ciple of resonance, sound a similar note in the 
second fork without the latter being struck. 
However, neither the fork nor the bell will actuate 
another fork or bell unless they are similar in 
every characteristic. 

A similar condition exists in radio and is a con¬ 
dition that must predominate in the thoughts of 
the experimenter who would be successful in his 
efforts. 


CHAPTER V 


PRACTICAL RADIO TELEGRAPHY 

In the brief history of radio found in the open¬ 
ing pages of this book, we have briefly discussed 
the earlier types of radio apparatus. While the 
principles explained in that chapter are still the 
principles underlying the radio art, in preparing 
any work upon the subject at this date, it would 
be a waste of the reader’s time to attempt to de¬ 
scribe apparatus which is no longer used in mod¬ 
ern practice, and in the following pages, except 
where the old time equipment may be useful in 
an explanatory sense, we shall describe only 
radio telegraph apparatus in general use to-day. 

Sparh Transmitters .—Electric waves, by 
means of which radio communication is carried on, 
are produced by transmitting apparatus. Power 
must be supplied by some kind of electric gen¬ 
erator, this must be converted into high fre¬ 
quency currents which flow in the transmitting 
aerial and cause electric waves which travel out 
through space. The waves may be damped or 
undamped, and we shall take each in turn. 

64 



Fig. 21. Complete standard inductively-coupled 
set, installed on shipboard 











RADIO TELEGRAPHY 


65 


Damped waves emanate from what is known as 
“spark’’ transmitters, while undamped waves are 
emitted from arc, high frequency alternators or 
vacuum tube sets, and are also known as con¬ 
tinuous wave transmitters. 

Discussing first the damped type of wave. 
Damped waves consist of groups or trains of 
oscillations repeated at regular intervals, the 
amplitude of the oscillations in each train decreas¬ 
ing continuously. The number of these trains of 
waves per second is some radio frequency. 
When such waves strike a receiving apparatus 
(hereafter described), they cause a tone in the 
telephone receiver. Signals are produced by 
means of a sending key, which permits the oper¬ 
ator to let trains of waves go for a short length 
of time, making a dot, or a longer period, making 
a dash. 

As above stated, it is our intention to first deal 
with the propagation of damped waves, as the ap¬ 
paratus is simple and easily adjusted, but the 
principles of damped and undamped waves are 
the same in many respects, so that much of what 
is described regarding damped wave apparatus 
applies to undamped waves as w^ell. 

Damped oscillations are produced when a con¬ 
denser discharges in a circuit containing induct- 


66 


RADIO 


ance. The condenser is discharged by placing it 
in series with a spark gap and applying a voltage 
to it high enough to break down or spark across 
the gap. However, the oscillations thus pro- 



Fig. 14. Simple spark discharge circuit. 


duced in such a circuit when the condenser dis¬ 
charges are “damped,” and soon die out. 

Methods of producing a regular succession of 
such condenser discharges in such a circuit are 
explained in the following. A high voltage must 
be applied to the condenser at regular intervals. 
This is done by means of a transformer. Through 
the primary of the transformer is passed either 
an alternating current or a current regularly in¬ 
terrupted by a vibrator, the latter being known 
as an induction coil. However, the induction coil 



















RADIO TELEGRAPHY 


67 


is seldom used in latter day radio, and the prin¬ 
ciple is best studied by the alternating current 
method. 

In Fig. 14, P and S are the primary and second¬ 
ary, respectively, of a step up transformer which 
received power from an alternating current gen¬ 
erator. The primary may be wound for 110 
volts, and the secondary for 5,000 to 20,000 volts. 
That is to say, that from a source of 110 volts 
supplied to the primary of the transformer, an 
induced emf. of from 5,000 to 20,000 volts will 
be produced in the secondary of the transformer. 
From this high voltage the condenser, marked C, 
is charged and stores up the energy. When the 
voltage becomes great enough it breaks down the 
spark gap and the discharge takes place as an 
oscillatory current in the inductance coil, marked 
L, and its leads. The main discharge does not 
take place through the turns of the transformer 
secondary on account of its relatively high im¬ 
pedance. In this connection, it may be said that 
modern sets are still further protected from con¬ 
denser discharge by inserting choke coils (not 
shown in Fig. 14) in the leads between the trans¬ 
former and the condenser. These obstruct the 
high frequency current, but do not hinder the pas¬ 
sage of the low frequency charging current into 


68 


RADIO 


the condenser. Fig. 15 shows a typical alternat¬ 
ing current transformer used in small radio sets. 

The standard generator frequency used in mod¬ 
ern practice is 500 cycles per second. This 



Fig. 15. Closed core transformer. 


causes the condenser to discharge 1,000 times per 
second, once for each positive and negative maxi- 











































































































































































































RADIO TELEGRAPHY 


69 


mum, or half cycle, if the spark gap is of such 
length as to break down at the maximum voltage 
given by the transformer. The number of sparks 
per second is called the “spark frequency.” 
With this standard spark frequency of 1,000 per 
second the amount of power the set sends out is 
considerably greater than it would at a low fre¬ 
quency of, say, 60 cycles or 120 alternations per 
second, because the transmitted radio waves are 
more nearly continuous. 

The radiated wave trains strike a receiving 
antenna more frequently and their amplitude does 
not need to be so great to produce the same effect 
as stronger waves received at longer intervals 
of time. The higher frequency produces a musi¬ 
cal tone in the receiving telephones that is more 
easily heard, because the average ear is most 
sensitive to sound waves of about 1,000 per sec¬ 
ond and also the tone is more easily heard through 
atmospheric disturbances or “static.” However, 
a 60 cycle supply may be used if the number of 
sparks per second is increased by utilizing what 
is known as a rotary spark gap giving several 
sparks per second, which multiplied by the alter¬ 
nations of the A C, produces a high musical tone 
similar in sound to the 500 cycle note. 

Each condenser discharge produces a train of 


70 


BADIO 


oscillations in the circuit, and each train of oscilla¬ 
tions consists of alternations of current which 
grow less and less in amplitude. 

Condensers .—Before discussing the means 
of getting the oscillations into an antenna, we 
should discuss the apparatus used in generating 
the oscillations, first taking the condenser unit. 
The most common types of condensers used in 
radio apparatus use mica or glass as the dielec¬ 
tric, with tinfoil or thin copper plating as the con¬ 
ducting coatings. Condensers with a compressed 
air dielectric are sometimes used, indeed, this type 
is considered the most perfect, but is seldom used 
owing to its bulkiness. For very high voltages the 
condenser plates are immersed in oil to prevent 
brush discharge. For some sets using moderate 
voltages, glass jars covered with tinfoil, or a cop¬ 
per coating, are sometimes used. This type of 
condenser is known as a * ‘leyden’ ’ jar. In this 
type paraffin wax is coated over the glass at the 
edges of the metal to prevent brush discharge. 

SparJe, Gap .—When the gap is broken down 
by the high voltage delivered from the trans¬ 
former, it becomes a conductor, and readily allows 
the oscillations of the condenser discharge to pass. 
During the interval between discharges the gap 
cools off (if properly constructed), and quickly 


RADIO TELEGRAPHY 


71 


becomes non-conducting again, allowing the con¬ 
denser to store another charge of energy. If the 
gap did not resume its non-conducting condition, 
the condenser would not charge again, since it 



Fig. 16. Plain spark gap. 


would be short-circuited by the gap, and further 
oscillations could not be produced. This restora¬ 
tion of the non-conducting state is called ‘ ‘ quench¬ 
ing.” A device called the “quenched gap” for 
very rapid quenching of the spark is described 
below. 

What is known as a plain gap consists of two 
metal rods so arranged that their distance apart 
is closely adjustable (See Fig. 16). It is impor¬ 
tant that the gap be kept very cool or it will arc; 
for that reason metal balls are sometimes used 
on the sparking ends of the rods in order that the 
sparking surfaces be ample. Sometimes these 
electrodes have protruding flat surfaces or fins 






















72 


RADIO 


for radiating away the heat. An air blast across 
the gap will greatly aid the recharging by remov¬ 
ing the ionized air or gas which is present after 
each gap discharge and if not removed is the 
cause of arcing. At the sparking surfaces an 
oxide slowly forms which being easily removed in 
the case of zinc or magnesium, is not very trouble¬ 
some. With other metals in general for gaps the 
oxidation is serious and is rapid enough to make 
operation unstable and inconvenient, requiring 
constant attention and adjustment. 

With a given condenser, the quantity of elec¬ 
tricity stored on the plates at each charging is 
proportional to the voltage impressed, and this 
can be regulated by lengthening or shortening the 
spark gap to obtain a higher or lower voltage at 
the beginning of the discharge. The length of 
the gap which can be employed is limited by the 
voltage that the transformer is capable of pro¬ 
ducing, the ability of the condenser dielectric to 
withstand the voltage, and the fact that for read¬ 
able signals the spark discharge must be regular. 

If the gap is too long, sparks will pass at only 
irregular intervals, also the condenser will be en¬ 
dangered and is liable to be punctured. If the 
gap, on the other hand, is too small it may arc 
and burn the electrodes and cause arcing at the 


RADIO TELEGRAPHY 


73 


gap. Arcing also causes a short circuit of the 
transformers, and the heavy current that flows 
interferes with the high frequency oscillations. 
An “arcy” spark gives a yellowish color and is 
easily distinguished from the bluish white, snappy 
sparks of normal operation. 

Even if no arc takes place the voltage is reduced 
by using too short a gap and this results in re¬ 
duced power and range. The length for smooth 
operation can usually be determined by trial, and 
is adjusted when a nice fat spark with the above 
mentioned bluish white appearance and snappy 
sound is obtained. 

The best spark gap is known as the “ quenched 
gap.” It has been found that a short spark be¬ 
tween cool electrodes is quenched very quickly, 
the air becoming non-conducting almost immedi¬ 
ately after it is broken down, or as soon as the 
current falls to a low value. This action is also 
improved, if the sparking chamber is air tight. 
The standard form of quenched gap consists of 
a number of flat copper or silver discs of fairly 
large surface, say seven to ten centimeters in 
diameter at the sparking surface, with their faces 
separated by about two-tenths of millimeter. To 
provide the necessary total length of gap for high 
voltage charging, a number of these small gaps 


74 


RADIO 


are put in series so that the spark must jump them 
all, one after the other. These discs are insulated 
and separated from each other by rings of mica 




Fig. 17. Quenched spark gap. 


or paper specially prepared with certain insulat¬ 
ing compounds. For an illustration of an assem¬ 
bled gap see Fig. 17. This gap is cooled by either 
an air blower attached, when the power used is 
high, or by copper flanges, acting as heat radi- 













RADIO TELEGRAPHY 


75 


ators when the power is small or moderate. The 
number of discs or gaps used is determined by 
the voltage, usually allowing 1,200 volts for each 
gap. 

The quenched gap is not used in gaps having a 
supply voltage as low as 60 cycles per second. 
The sparks obtained at that frequency are found 
to be irregular and not of a good tone. For this 
60 cycle source of supply a rotary gap is mostly 
used and is described below. For 500 cycle fre¬ 
quency the quenched gap is adjusted to break¬ 
down at the maximum value of the applied volt¬ 
age ; that is, with its total length so adjusted as to 
give one spark for each half cycle or alternation 
of the electromotive force. Discharges at other 
times are not possible; and as a result of this 
regularity a clear note is obtained. This 
quenched gap is considered standard and the most 
efficient type of gap for power up to about 10 
kilowatts. The great advantage of the quenched 
gap is that it is a great aid to the production of 
a “pure” wave, which is discussed later in this 
work. Another excellent quality of the quenched 
gap is the fact that it is practically noiseless, on 
account of the short gap between discs and that 
it is enclosed. On the other hand a plain and 
rotary gap makes an awful noise. 


76 


RADIO 


A rotary gap usually consists of a wheel with 
projecting points with a stationary electrode on 
each side of the wheel, as shown in Figure 18. 
The spark jumps from one stationary electrode 
to one of the moving points, flows across the 
wheel, and then, after leaping from the cor¬ 
responding point on the opposite side of the 
wheel, passes the gap between wheel and electrode 



Fig. 18 . Non-synchronous spark gap. 


tc* the second stationary electrode. The number 
of sparks per second is determined by the speed 
of the wheel, which is motor driven, or by the 
number of revolving points or studs. A rheostat 
is generally introduced in the circuit operating 
the motor, in order to control its speed and thus 
adjust the gap to any pitch or tone desired. There 
are many forms of rotary gaps, however, their 



















RADIO TELEGRAPHY 


77 


principles are similar and the results obtained 
more or less uniform according to their design 
and operation. This type of gap is divided 
sharply into two groups, “non-synchronous” and 
“synchronous.” 

In the case of a 4 4 synchronous ’ 9 rotary gap the 
speed is so maintained as to bring the knobs or 
studs near together at just the moment when the 
alternating voltage upon the condenser reaches 
its maximum value, either positive or negative. 
Thus 500 cycles will produce 1,000 sparks per sec¬ 
ond. This regular occurrence of the discharge 
gives smooth and efficient operation, and a pure 
musical tone. The synchronizing is made pos¬ 
sible by attaching the rotating element or wheel 
of the spark gap to the shaft of the alternator 
which supplies the electromotive force which in 
turn charges the condenser. A gap not so ad¬ 
justed to the peak of the A.C. is called non-syn- 
chronous. 

As in the case of attempts to quench a 60 cycle 
source of emf., attempts to synchronize this 
source of supply by a synchronous gap giving, for 
example, 6 sparks per alternation or half cycle, 
have not given satisfaction, because the applied 
voltage is not the same at the time of the different 
sparks, and while the note is of high pitch, it is 


78 


RADIO 


not musical. Thus it is found better practice to 
use a non-synchronous gap in such a case, pro¬ 
ducing a large number of sparks per second and 
letting them occur whenever they may happen 
during the entire cycle. The irregularities will 
somewhat balance up. While sometimes the tone 
is not strictly musical, it can, by means of the 
motor control or additional points or studs, be 
made of high pitch. The non-synchronous gap is 
best used if nothing but a 60 cycle or other low 
frequency source of emf. is available. Such 
low frequencies are now being avoided in com¬ 
mercial radio practice and as has been stated be¬ 
fore, the standard is 500 cycles. In amateur cir¬ 
cles, however, 60 cycle is often the only source of 
supply available and rotary gaps are very de¬ 
sirous in that field. 

Radiotelegraph Transmitters. —Hav¬ 
ing discussed the most important units found in a 
transmitter, we will now turn our attention to a 
complete radio telegraph equipment. As previ¬ 
ously explained, it is intended that the earlier 
types mentioned in the historical reference of this 
work will not be discussed. Although they form 
the simplest form of transmission and are eco¬ 
nomical in design for a beginner to construct, their 
use is forbidden in the U. S. A. for the following 


RADIO TELEGRAPHY 


79 


reasons. In 1912 certain laws and regulations 
were adopted by Congress to control radio tele¬ 
graphic communication. A regulation which defi¬ 
nitely fixed the type of transmitter that should 
be used, was one stipulating that a pure wave 
should be emitted, and that no equipment with a 
decrement value greater than two tenths would 
be permissible. 

The earlier transmitter, known as plain aerial, 
could not emit such a wave and propagated a 
wave verv broad in its characteristics. It was a 
good radiating system but the waves emitted are 
of such high decrement that they cannot be read¬ 
ily tuned out in receiving apparatus when one 
does not desire to receive them. This type would 
emit a wave with what is known as several 
“humps ’’ and would be heard in a receiver on 
a number of different wave lengths thus causing 
much “jamming’’ or “interference.” Its only 
advantages besides simplicity are its effective¬ 
ness in cases where the sending operator wants 
all possible stations to hear him, as for instance, 
when a ship needs help, or in war time when it is 
desired to drown out the enemy’s signals. 

Inductively Coupled Transmitters .— 
As it is impossible for the above mentioned rea¬ 
sons for the experimenter tc use any equipment 


80 


KADIO 


which will not comply with governmental regula¬ 
tions, we shall turn our attention to the only prac¬ 
tical types, which are known as “inductively 
coupled’’ transmitters, and for illustrative pur¬ 
poses describe a standard equipment using a 500 
cycle source of power and a quenched gap. This 
equipment can be modified to utilize lower fre¬ 
quencies as a power source and other types of 
gaps, such as previously described. 

Every inductively coupled spark transmitter is 
divided into four circuits which are designated as 
follows:— 

1. The low frequency, low potential circuit 
which includes all apparatus from the supply of 
alternating current to the low voltage supplied 
to the primary winding of the power transformer. 
Included is a telegraph key to make or break the 
circuit. 

2. The low frequency, high potential circuit, 
which includes the secondary or high voltage 
windings of the power transformer and the con¬ 
densers. 

3. The high frequency, high potential, closed 
oscillating circuit including the condensers, the 
primary winding of the oscillation transformer 
and the spark gap. 


RADIO TELEGRAPHY 81 

4. The high frequency, high voltage oscillatory 
circuit, which includes the secondary winding of 
the oscillation transformer, also antenna in¬ 
ductance. 

Sometimes in commercial equipment a series 
condenser is inserted in this circuit to reduce the 
fundamental wave length, enabling the apparatus 
to transmit on 300 meters, thus complying with 
a governmental requirement. 

The action of this transmitter is as follows:— 

Having a source of alternating current, when 
we depress the telegraph key mentioned in circuit 
numbered one, this alternating current flows in a 
circuit from the alternator windings through the 
primary windings of the power transformer and 
back to the generator. When the lever of the key 
is raised the circuit is broken. By means of this 
key, this primary circuit is made and broken, gen¬ 
erally in the shape of the familiar dots and dashes 
of the Morse Code. Bearing in mind the preced¬ 
ing chapter devoted to electro-magnetism, the fol¬ 
lowing action takes place in the circuit. 

As the key is depressed and releases, the alter¬ 
nating current flowing through the primary wind¬ 
ing of the power transformer sets up magnetic 
lines of force which rise and fall, and also re¬ 
verses in unison with the alternating current, 


82 


BADIO 


which has previously been described as one which 
alternates in its direction of flow. 

These lines of force in turn cutting the wind¬ 
ings of the secondary or high potential windings 
of the power transformer builds up a high voltage 
in that circuit, which we have described as num¬ 
ber two. The increase in this voltage is propor¬ 
tional to the ratio of turns. For example, if 
there were ten turns in the primary, and one hun¬ 
dred turns in the secondary, the secondary volt¬ 
age would be ten times as great as the primary 
voltage. The alternating current voltages usually 
employed are from 110 to 250 volts, thus giving 
a secondary voltage of from 10,000 to 25,000 volts. 
The primary winding generally consists of com¬ 
paratively few turns of heavy wire, while the 
secondary is built up of a great many turns of 
fine wire. The number of turns employed de¬ 
pending upon the voltage desired and the type of 
spark gap utilized. With a 500 cycle, quenched 
gap set, the secondary voltage is relatively small. 

The high voltage from the secondary circuit of 
the transformer is then delivered to a condenser, 
the construction of which we have previously dis¬ 
cussed. This energy is then stored in the con¬ 
denser until a point is reached when the condenser 
can hold no more, and the electro-static charge 


EADIO TELEGEAPHY 


83 


thus accumulated is discharged across the spark 
gap, creating an oscillating circuit in the circuit 
we have described as number three. This circuit 
is generally alluded to as the closed oscillatory 
circuit. These oscillations are of radio fre¬ 
quency. Eadio frequencies are those above the 
range of audibility and are generally considered 
frequencies above 10,000 cycles per second. 

We have explained in the previous explanatory 
chapter on radio that this radio or wave fre¬ 
quency depends upon the characteristics of the 
sending circuit, in this case the frequency of the 
oscillations in the closed oscillatory circuit would 
depend upon the amount of capacity and induct¬ 
ance; in other words, it would depend upon the 
size of the inductance coil and the condenser and 
may be anywhere from 1,000,000 to 2,000,000 per 
second. It is customary to construct apparatus 
wherein it is possible to vary the inductance and 
capacity. This can be done by varying either or 
both but in modern practice it is usual to use a 
certain fixed condenser and make the inductance 
variable, thus permitting a convenient method of 
changing wave lengths. This inductance will de¬ 
pend upon the number of turns in the wire and the 
diameter of the turns. 

Having developed by the foregoing means, 


84 BADIO 


oscillations in the closed oscillatory circuit, these 
are now transferred from the primary windings 



Fig. 19. Oscillation transformer. The secondary 
moves up and down the rod, inside the primary. 













































































































EADIO TELEGEAPHY 85 

of the oscillation transformer, in circuit number 
three, to the secondary windings of the oscilla¬ 
tion transformer in the open oscillatory or as it is 
also known, the antenna circuit, which have been 
previously alluded to as circuit number 4. This 
oscillation transformer (Fig. 19) is just what its 
name implies, and is a device for transferring 
energy (in this case radio frequency current) 
from one circuit to another, this being done by 
means of magnetic coupling, just as the low poten¬ 
tial alternating current was transferred by means 
of the power transformer from circuit 1 to cir¬ 
cuit 2. While these radio frequency oscillations 
are flowing in the oscillation transformer primary 
they set up magnetic lines of force about it, in 
the manner described in the chapters dealing with 
magnetism and electromagnetism. These mag¬ 
netic lines of force cut the secondary windings 
of the oscillation transformer in circuit 4, induc¬ 
ing therein a current of the same frequency. As 
these oscillations travel the windings of the sec¬ 
ondary and the remainder of the open oscillatory 
circuit, or, in other words, circuit number 4, elec¬ 
trostatic and electromagnetic strains are set up iri 
the surrounding ether and thus these disturb¬ 
ances give rise to the radio waves, which are 


86 


RADIO 


propagated into space at the speed of light, 186,- 
000 miles per second. 

A complete diagram of tlie above described 
transmitter will be found in Fig. 20. 

Tuning and Resonance .—Having traced 



Fig. 20. Inductively-coupled transmitting circuit. 


the electrical energy through the above mentioned 
transmitter and shown how low frequency alter¬ 
nating current is converted to radio frequency 
oscillations, also the method of propagating this 
energy into ether waves, we must now study the 
phenomenon of resonance, which will show us the 
necessity of placing the closed and open oscillat¬ 
ing circuits in ‘ ‘ tune 9 9 in order that the maximum 
of energy may be transferred from one to the 
other. Not only must this be done to obtain a 
maximum of efficiency, but also that we may ob- 













RADIO TELEGRAPHY 87 

tain a “pure wave” and thereby conform to the 
above mentioned laws and regulations. 

A very pronounced maximum of current in the 
open or antenna circuit is obtained when its nat¬ 
ural period of oscillation is the same as that of 
the primary circuit. This occurs when the sec¬ 
ondary or antenna inductance and capacity equals 
the primary inductance and capacity. The in¬ 
ductance in the antenna circuit includes the an¬ 
tenna itself, the lead in wire, the secondary wind¬ 
ings of the oscillation transformer, and, if one 
is used, the additional antenna inductance coil, or 
as it is also known, the “loading coil.” It is im¬ 
portant that the wiring between the units in the 
closed oscillating circuit be as short as possible, 
therefore with the leads so short almost all the 
inductance is in the primary windings of the 
oscillation transformer, also as the capacity of 
the condenser in that circuit is large, most of the 
capacitance is contained in that unit. As previ¬ 
ously explained, the condenser unit in this circuit 
generally has a fixed value, and the inductance 
made variable to provide easy adjustment. The 
additional inductance coil (if used) and the sec¬ 
ondary windings of the oscillation transformer in 
the open or antenna circuit are invariably made 
variable. 


88 


RADIO 


To obtain resonance between the closed and 
open oscillatory circuits the following simple pro¬ 
cedure may be used. Only two instruments will 
be required to obtain results, a wave-meter and 
a hot-wire ammeter, which are both fully de¬ 
scribed in the pages devoted to “Definitions.” 

We will assume that the desired wave length 
required is to be 600 meters. 

The coupling between the open and closed oscil¬ 
lating circuit should first be as far apart as pos¬ 
sible and the antenna and ground disconnected 
from the secondary of the oscillation transformer. 
The wavemeter should be placed first in close 
proximity to the primary of the oscillation trans¬ 
former. A rough calculation of the number of 
turns of primary inductance should be made, which 
would give the desired wave length. Oscillations 
should then be set up in the closed circuit by de¬ 
pressing the key. A reading of the wavemeter 
will then determine the wave length of the closed 
circuit. If the first rough calculation was incor¬ 
rect, and the desired wave length not found, it 
will be easy to add or reduce the number of turns 
of inductance as required, according to whether 
the wavemeter has indicated a wave length shorter 
or longer than that required. Several adjust¬ 
ments of this description will eventually enable 


RADIO TELEGRAPHY 89 

the operator to obtain the desired wave. In this 
method of tuning, it will be found desirable, for 
better results, to make the indicated wave length 
of the primary oscillating circuit slightly lower 
than that which is required for working purposes, 
as it is found in practice that when the open and 
closed circuits are coupled the wave length of the 
transmitter will slightly increase over that indi¬ 
cated in the primary reading. A better wave- 
meter reading will sometimes be available if the 
wavemeter is withdrawn from too close proxim¬ 
ity to the coil, until the indication is at a mini¬ 
mum value. If this withdrawing is done undis- 
turbingly, a reading may be observed while the 
motion is taking place, or readings taken at vari¬ 
ous distances. This will tend to greater ac¬ 
curacy. 

Having adjusted the closed circuit to the de¬ 
sired wave-length, the antenna and ground con¬ 
nections should then be re-connected to the open 
oscillatory circuit. The hot-wire ammeter should 
be placed in series between the ground and the 
secondary of the oscillation transformer. Hav¬ 
ing separated, as far as possible, the primary and 
secondary coils of the oscillation transformer dur¬ 
ing the previous adjustments, these two coils 
should now be brought somewhat closer together. 


90 


RADIO 


An arbitrary adjustment of the secondary of 
the oscillation transformer can be made, bring¬ 
ing all its turns into the circuit, unless perhaps 
the natural period of the antenna is so large that 
it is necessary to reduce the amount of inductance 
to obtain the desired wave length, in that event 
it would be necessary to carefully adjust the num¬ 
ber of turns needed by means of the wavemeter. 
In this connection it is well to note that a station 
is generally built with some definite object in 
mind, and that the antenna is generally so con¬ 
structed that its natural period is considerably 
less than the wave length to be utilized. An ar¬ 
rangement that gives excellent results is to figure 
in constructing the antenna to have it with a nat¬ 
ural period or fundamental wave length of ap¬ 
proximately two-thirds of the wave length it is 
desired to radiate. This allows, as a rule, the 
full secondary of the oscillation transformer to 
be utilized, it also permits us to use an antenna 
loading coil to tune to resonance and maximum 
radiation. Of course in many circumstances this 
may not be feasible and we must govern the ad¬ 
justment of the open circuit accordingly. 

Having joined the antenna and ground connec¬ 
tions to the secondary of the open circuit, another 
reading of the wavemeter should be taken. It is 


RADIO TELEGRAPHY 


91 


possible that some slight readjustment of the pri¬ 
mary of the oscillation transformer may be neces¬ 
sary to obtain the exact wave length desired. 

Having by means of the wavemeter accom¬ 
plished this, the next step is to obtain maximum 
radiation. This is done by adding or reducing 
the number of turns in the aerial loading induct¬ 
ance. A few trials either way will soon show, 
by reading the hot-wire ammeter, when this 
maximum is reached. If a hot-wire ammeter is 
not available, a flashlight electric lamp of about 
4 volts may be placed in series with the ground 
connection, and maximum radiation is denoted 
when this lamp lights up brightest. 

The next step is to adjust the coupling between 
the primary and secondary of the oscillation 
transformer, in order that the wave emitted com¬ 
plies with the regulations. This may be accom¬ 
plished by means of the wavemeter. Having 
coupled the two circuits to obtain maximum radi¬ 
ation, a wavemeter reading should be taken, cov¬ 
ering the entire range of the wavemeter range. 
It is possible, indeed probable, that it will be 
found that two or even more waves will appear. 
The coupling in that case must be opened until it 
is noted only one point of resonance, or one 
“hump” appears, and that on the desired wave 


92 


RADIO 


length. A readjustment of the loading coil for 
maximum radiation should again be made and 
then another wavemeter reading of the coupling 
taken. 

Relation of Sparfc Gaps to Reso¬ 
nance .—In the matter of coupling, it will be 
found that the type of spark gap used is a big fac¬ 
tor. It is desirable to have as sharp a resonance 
curve or as pure a wave as possible, hence it will 
be found that a very loose coupling will be found 
necessary when a plain spark gap is used. On 
the other hand, a synchronous rotary gap or a 
quenched gap permits a closer coupling and gen¬ 
erally speaking a greater transfer of energy from 
the closed to the open circuits. 

The action of the quenched gap is to open the 
primary circuit by the suppression of the spark 
at the end of its first train of waves. This pre¬ 
vents the secondary from inducing oscillations in 
the primary again, that is, from re-transferring 
energy back to the primary. The secondary or 
antenna oscillations are not thereafter interfered 
with by the primary and the antenna goes on 
oscillating until the energy is all dissipated as 
waves or heat. The length of the train will de¬ 
pend only upon the decrement of the antenna cir¬ 
cuit. By reducing the resistance, the dielectric 


RADIO TELEGRAPHY 


93 


losses, the brush or corona discharges and other 
leakage, the antenna current may be made to 
oscillate for a comparatively long time, at the fre¬ 
quency for which the set was adjusted. This 
rapid or sudden quenching of the primary avoids 
double waves, even with close coupling. In fact, 
the coupling should be close for good operation 
with the quenched gap. Great care must be 
taken with the adjustment of the coupling, hut 
it is well worth the care, as it gives a high pitched 
clear note when properly adjusted. As previ¬ 
ously pointed out, the wavemeter will readily 
show when a single sharp wave is obtained, and 
the sound in the telephone receivers will indicate 
the proper adjustment for a good note. 

It is well to note that the principles of opera¬ 
tion of the quenched gap and the plain gap are 
exactly opposite. The former aims to stop the 
primary oscillations quickly, after the secondary 
has been brought to full activity. The latter aims 
to keep the primary oscillations going as long as 
possible, all the time giving energy to the sec¬ 
ondary as it is radiated away; the coupling is 
loose and primary decrement is kept low. The 
rapid decrease of the oscillations in a quenched 
gap circuit are assisted by having a large ratio 
of capacitance to inductance. This has the inci- 


94 


EADIO 


dental advantage that the voltages across the con¬ 
denser and coil are thus kept low. 

Damping and Decrement .—If the energy 
in the antenna circuit is dissipated at too rapid a 
rate, owing‘either to radiated waves or heat losses, 
the oscillations die out rapidly and not enough 
waves exist in a received train to set up oscilla¬ 
tions of a well defined period in a receiving an¬ 
tenna. Such waves are strongly damped and have 
a large decrement. They produce received cur¬ 
rents of about the same value for a considerable 
range of wave lengths. Thus selective tuning is 
not possible. To increase the number of waves 
sent out in each wave train from the open circuit, 
that is, to make the oscillations last longer, the re¬ 
sistance of the circuits must be kept low. When 
using a plain gap the coupling between closed and 
open circuits must be small enough not to take 
energy too fast from the closed oscillating circuit. 
At each condenser discharge the primary has a 
train of oscillations which at best die out long 
before another train starts, these oscillations are 
stopped more quickly, however, if the energy is 
drawn rapidly out of the circuit by the antenna. 
Close coupling is permissible only when a 
quenched gap is used, as previously explained. 
With any other kind of gap, the secondary is kept 


RADIO TELEGRAPHY 95 

oscillating by energy continually received from 
the primary. 

A great many factors contribute to the resist¬ 
ance of the antenna circuit, and this must be kept 
as low as possible. The antenna must have a 
good, low resistance ground, must use wires of 
fairly low resistance, must not be over trees or 
other poor dielectrics. The resistance of the 
closed oscillatory circuit must be very low. Heav¬ 
ier currents flow there than in antenna wires. 
For this reason the closed circuit wires must be 
short and of large surface, preferably stranded 
copper wires or copper tubing should be used. 
The condenser should be a good one, free from 
power loss. 

Changes of Wave Length .—In many sets 
of apparatus it is customary to have connections 
arranged by which different chosen wave lengths, 
say 300 or 600 meters, can be transmitted without 
the necessity of a readjustment of the apparatus 
after each change and also permits of a rapid 
change-over from one wave length to the other. 

An antenna alone, without any inductance coil 
has a natural wave length of its own, dependent 
upon its inductance and capacitance. The antenna 
as a rule is so designed that its natural wave 
length is shorter than the wave length to be used, 


96 


BADIO 


and the wave length is brought up by adding in¬ 
ductance in series or merely by added inductance 
of the secondary of the oscillation transformer. 

In the case of a small antenna, such as that on 
a small vessel, it is necessary to use a large an¬ 
tenna inductance. Since it is desirable to have a 
convenient method of coupling the closed and 
open oscillating circuits, in order that fairly criti¬ 
cal adjustments may be made, a part of this sec¬ 
ondary inductance can be in a separate coil called 
the antenna “loading coil.” This is connected to 
the secondary of the oscillation tranformer in 
series with the antenna. For a quick change of 
wave lengths, the apparatus can be designed so 
that by means of a switch with a mechanism of 
levers, changes simultaneously the adjustments of 
all three coils. From these coils are taken out taps 
over which three switch blades pass, adjusting all 
three inductances to the values needed for the par¬ 
ticular wave length desired, keeping the circuits in 
resonance. However, a change of coupling may 
be necessary for each change. This can be deter¬ 
mined by tests and the change of coupling, if 
necessary, marked on the apparatus for the 
operator’s guidance. 

In the event that the natural period of the 


RADIO TELEGRAPHY 


97 


antenna is greater than the wave length it is 
desired to work with, an arrangement can be 
made as follows: 

In the lead between the secondary of the oscil¬ 
lation transformer and the ground a condenser 
should be placed in series. This must be capable 
of withstanding high voltages similar to those in 
the main transmitter. By using a small capaci¬ 
tance the wave length can be reduced to approach 
one-half of the natural wave length. It should 
not be reduced that much, however, for the radia¬ 
tion of the set would be inefficient if the condenser 
is too small. 

Over-all Efficiency .—To maintain good 
efficiency all resistance in the circuits must be 
kept as low as possible. A number of sugges¬ 
tions have been offered in the preceding pages 
which will do much to accomplish this. 

It is very necessary to avoid brush discharges 
or corona losses and arcing. Keep all connec¬ 
tions tight, condenser plates and other parts of 
the circuits free from dust and moisture. It is 
most important that the antenna be well insulated. 
Brush discharge may be curtailed by eliminating 
sharp edges or points on conductors, and by coat¬ 
ing the edges of metal condenser plates with 


98 


RADIO 


paraffin wax. The guy wires of an antenna should 
be divided into short lengths and strain insulators 
placed between each length to reduce the flow of 
current in the guys. Inductance coils must be 
properly designed, the wire or copper ribbon of 
which they may be constructed must have suffi¬ 
cient surface to carry the high potential they 
must handle. Unless this is done, great loss is 
caused by heating. The proper design of the 
spark gap is most essential. 

Impulse Transmitters .—The apparatus 
we have dealt with in the preceding pages is known 
as the four circuit transmitter, and as we have 
shown, requires critical adjustment between the 
various circuits. There is, however, another type 
of inductively coupled transmitter in commercial 
use which is known as the ‘‘impulse ’ 9 transmitter. 
This type was developed by Mr. R. E. Thompson, 
an American radio engineer who for many years 
was in the United States Government service, and 
the transmitter bears his name. Apparatus sim¬ 
ilar in principle is also marketed by several manu¬ 
facturers, all operate under the principles of the 
Lodge patent, alluded to in the chapter devoted to 
historical reference (Figs. 22 and 23). 

Briefly described, the action and characteristics 
of this transmitter are as follows: 



Fig. 23. Complete installation, impulse type 

transmitter 







































RADIO TELEGRAPHY 99 

In the above described set, it was shown how the 
primary windings of the oscillation transformer 
consisted of numerous turns of wire and was vari¬ 
able. In the impulse type this is the reverse and 
the primary is fixed, as also is the condenser, 
which contrary to the 4-circuit variable type, is 



Fig. 22. Circuit diagram impulse transmitter. P S, 
transformer. C, condenser. Q, quenched gaps. L and 
L 2 , primary and secondary oscillation transformer. C 2 , 
short wave condenser. L 3 , antenna loading inductance. 
A, ammeter. 

of a very high capacity. The spark gap consists 
of two high resistance units of high resistance. 
Taken throughout the closed circuit inductance is 
kept at minimum. Wherever possible leads and 
connecting wires are done away with. This is 
carried to such an extent that the gaps and con¬ 
densers are mounted directly on the panel board 


) > » 


> 














100 


RADIO 


and from them is taken a single loop of heavy 
wire or tubing as an oscillation transformer or 
primary, or, it may be termed a transfer agency. 
This arrangement permits of only one wave 
length in the closed circuit. As this type of trans¬ 
mitter has been used exclusively on shipboard, 
where the range of wave lengths is arbitrarily 
fixed by regulations, the wave length of the closed 
circuit is generally fixed about 700 meters. 
The open or antenna circuit is similar 
in design to the previously described set, 
and bearing in mind that the closed cir¬ 
cuit wave length remains constant, this antenna 
can be tuned to wave lengths varying from 600 
to as low as 200 meters without a change in the 
closed circuit. This makes the impulse trans¬ 
mitter a non-resonant one. The action in actual 
transmission is best described by the use of a 
well known analogy. Suppose we strike the ‘* C ’ ’ 
note on a piano, all other “C” notes in the instru¬ 
ment will respond in unison without being touched, 
but no other note will vibrate. This has been fully 
discussed under resonance in the explanatory 
chapter on radio in these pages. However, if 
we were to lift the piano and drop it, or give the 
case of the instrument a mighty blow with a heavy 
projectile, all the strings in the piano would re- 


RADIO TELEGRAPHY 


101 


spond and vibrate. Hence we find that although 
the strings of the piano vibrated with the blow, it 
was not because of any resonant relation between 
the blow and the strings, but because of the 
“kick” or “crack” imparted to them. Now, in 
the case of the impulse transmitter we find that 
the antenna circuit consisting of inductance and 
capacity, has a natural period of its own, and will 
oscillate at that period, depending upon the 
amount of capacitance and inductance contained 
therein. The closed circuit, however, is considered 
non-oscillatory, but given a large condenser dis¬ 
charge, it corresponds to the heavy blow or kick 
given the piano, and will cause the antenna to 
oscillate. This method of excitation is termed 
“impulse” excitation, “shock” excitation, or 
“whip-crack” excitation. 

One of the advantages of this type of apparatus 
is the absence of numerous adjustments. Having 
an arbitrary, steady, closed circuit, the only ad¬ 
justments necessary are those in the antenna cir¬ 
cuit. Within certain limits, it will radiate several 
wave lengths without any attempt at resonance. 

Undamped Wave Transmitters .—Un¬ 
damped oscillations are not broken up into groups 
like damped oscillations. Exactly similar current 
cycles follow one another continuously, except 


102 


RADIO 


as they are interrupted by the sending key, or 
subjected to gradual fluctuations of intensity as 
when used in radio telephony. Undamped oscilla¬ 
tions are produced by a high frequency alternator, 
an arc or by vacuum tubes. In this chapter we 
do not propose to take up transmission by vacuum 
tube, as this is treated in succeeding chapters 
covering vacuum tubes and radio telephony. 

The main advantages of undamped, or as they 
are also known (especially in Europe) continuous 
waves, are the following: 1. Extremely sharp 
tuning is obtained and consequent reduction of 
interference between stations working close to¬ 
gether. A slight change of adjustment throws a 
receiving set out of tune, and the operator may 
pass over the correct tuning point by too rapid 
a movement of the receiving adjusting dials. 
2. Radio Telephony is made possible. 3. Since 
the oscillations go on continuously instead of only 
a small fraction of the time, as in the case of 
damped waves, their amplitudes need not be so 
great, hence the voltages applied to the transmit¬ 
ting condenser and antenna are much lower. 
4. With damped waves the pitch or tone of 
received signals depends entirely upon the num¬ 
ber of sparks per second of the transmitter. 
With undamped waves the receiving operator con- 


RADIO TELEGRAPHY 


103 


trols the tone of the received signals, and this can 
be varied and made as high as desired, within 
certain audible limits, to distinguish it from “at¬ 
mospheric” or “static,” and to suit the sensitive¬ 
ness of the receiving operator’s ear and the tele¬ 
phones used in reception. 

These advantages, freedom from interference 
from other stations through selective tuning, the 
high tones and low voltages, and the greater free¬ 
dom from strays combine to permit of a higher 
speed of telegraphy than could otherwise be ob¬ 
tained with other classes of transmission. 

High Frequency Alternators .—The 
scope of this work, primarily intended for the use 
of readers unacquainted or with slight knowledge 
of the radio art, will not permit of a lengthy dis¬ 
cussion of this type of transmission. However, in 
conjunction with the other contents, a brief out¬ 
line of this, the latest form of radio-telegraphy, 
may prove of interest. 

For the production of continuous oscillations 
an alternating current generator of very high fre¬ 
quency can be used. Alexanderson and Gold¬ 
schmidt both developed alternators which gen¬ 
erate alternating currents of radio frequency. 
This alternator is connected directly or induc¬ 
tively to the antenna and ground, and constitutes 


104 


EADIO 


the simplest possible connection for producing 
continuous or undamped waves. However, to ob¬ 
tain a wave length of say 1500 meters, the fre¬ 
quency of the A.C. must be as high as 200,000 
cycles per second. The generator speed required 
to produce this frequency is so high that a special 
time of construction is necessary for such a 
machine. It is also necessary to secure apparatus 
for keeping the speed of the machine constant, 
so that the wave length will not change. This sys¬ 
tem is impossible for very short waves and there¬ 
fore arc and vacuum tube apparatus is utilized 
for the shorter wave lengths and less powerful 
stations. 

Goldschmidt employed a radio frequency alter¬ 
nator, with a “frequency changer/’ An initial 
A.C. of about 10,000, which by means of what is 
known as a “reflection” process, is changed 
to 40,000 cycles, giving a wave length of 7,500 
meters. 

The Alexanderson machine is one of great speed 
and many field poles, and frequencies as high as 
200,000 cycles are obtained. This radio fre¬ 
quency, which is impressed on the antenna cir¬ 
cuit, is actually taken from the terminals of the 
machine. 

Undoubtedly for long distance work employing 


RADIO TELEGRAPHY 


105 


very long wave lengths, these high frequency 
alternators will be used to a very large extent, in 
fact, the large radio corporations, competing with 
the submarine cables are using them to-day with 
most successful results. 

Are Transmitters .—The arc system of 
radio-telegraphy was invented by a Danish scien¬ 
tist, Yaldemar Poulsen. Much of the success of 
the system, however, can be claimed by American 
engineers employed by the Federal Telegraph 
Company of San Francisco, who acquired the 
American rights to Poulsen’s invention. Possibly 
the chief of these being Mr. C. F. Elwell. 

The method used for producing undamped 
waves of rather great wave length (generally over 
2,000 meters), is by means of a direct current arc 
operated on about 500 volts. It has been dis¬ 
covered that an electric arc between proper elec¬ 
trodes, shunted by an inductance coil and a 
condenser, will produce undamped oscillations 
through the shunt circuit. The operation is as 
follows: The current through the arc is always 
in the same direction but may vary in magnitude. 
It is found that when the current in the arc in¬ 
creases, the voltage at its terminals falls off. 
Suppose the arc to be burning steadily with the 
capacitance and inductance circuit disconnected. 


106 


RADIO 


If now that circuit is connected, the condenser 
begins charging with the left plate positive, and 
draws current away from the arc. The potential 
difference of the arc increases and helps the 
charging. The charging continues until the 
counter electromotive force of the condenser 
equals that of the applied. As the charging nears 
its end, the charging current becomes gradually 
less, and the arc current as a whole increases to 
its normal value, with a corresponding drop in 
voltage. The condenser then begins to discharge 
downward through the arc, increasing the arc 
current and lowering its voltage. Lowering the 
voltage across the terminals of the arc aids the 
condenser to discharge, and the effect of the induc¬ 
tance in the circuit tends to keep the current flow¬ 
ing and a charge is accumulated on the condenser 
plates of the opposite sign from the first one. As 
the charge now nears its end, the charging current 
downward through the arc becomes gradu¬ 
ally less, and the arc current decreases, 
causing the voltage to rise. It is seen that 
the rise of the direct current voltage is such 
as to attempt to charge the left plate of the con¬ 
denser positive, and the positive charges on the 
right hand plate begin at once to come back, going 
up through the arc and decreasing the current. 


RADIO TELEGRAPHY 


107 


There is a consequent further rise of voltage, and 
in a direction to assist first the condenser dis¬ 
charge, and then the recharge in the opposite 
direction (on the left hand plate). The action 
now begins all over again, and thus continuous 
oscillations take place through the circuit. 

The arc burns in a closed chamber having hydo- 
gen passing through. The positive electrode is 
of copper and the negative solid carbon, both being 
of large size and cooled by a water jacket. The 
key is arranged to short circuit some of the turns 
of inductance in the antenna circuit, the correct 
number of turns being adjusted for resonance 
with the key closed. Then with the key open, the 
antenna circuit is out of tune with the arc oscilla¬ 
tions and the current is negligible, thus forming 
the intervals between dots and dashes. 

Tuning Continuous Wave Sets .—With 
high frequency alternator apparatus the fre¬ 
quency and hence the wave length are determined 
by the speed of the generator and the number of 
poles. The inductance and capacitance of the an¬ 
tenna should be of such values as to give the cir¬ 
cuit the same natural frequency as the generated 
current. This is brought about by adjusting the 
antenna loading coil to give maximum current in 
the hot wire ammeter. 


108 


EADIO 


Much of the same method is used with arc sets. 
The desired wave length is obtained by adjust¬ 
ment of the condenser and inductance, the antenna 
circuit being opened, and the wave length being 
set on a wavemeter which is brought near. The 
antenna circuit is then adjusted to the same wave 
length by varying the loading coil until the hot 
wire ammeter gives a maximum reading. A pilot 
lamp can be substituted instead of the hot wire 
ammeter, since it can be adjusted by a shunt to 
light only when the circuits are in resonance. 
Sometimes this lamp is connected inductively by a 
loop of wire instead of being directly in the 
ground wire. 






. 





























CHAPTER VI 


RADIO RECEPTION 

Introductory .—Receiving sets are divided 
into two well defined classes, those for damped 
waves, and those for undamped waves. In mod¬ 
ern practice a receiver is so designed that, in¬ 
cluded in its general construction are methods for 
rapidly changing from damped to undamped re¬ 
ception and vice versa . 

Sets for damped wave reception in practice 
involve the simpler connections and form a good 
starting point for any explanation of the subject, 
although it will he found that later, in discussing 
undamped wave receivers, very slight modifica¬ 
tions of the damped wave apparatus will give one 
method of receiving undamped waves. Before 
proceeding with a discussion of the various receiv¬ 
ing circuits, it will be well to digress and explain 
the principles and construction of the individual 
units which comprise a receiving equipment. 

Crystal Detectors .—A very simple and 
convenient form of detector is obtained by the 

contact of two dissimilar solid substances, prop- 

109 


110 


RADIO 


erly chosen. The number of substances which 
have been found suitable for use in such detectors 
is large. This type of detector is easily portable, 
but requires frequent adjustment and is less sensi¬ 
tive than the vacuum tube. 

Among the combinations of solid substances 
which have been used as contact detectors may be 
jnentioned silicon with steel, carbon with steel and 
tellurium with aluminum. The most important 
contact detectors, however, are crystals, natural 
or artificial, in contact with a metallic point. 
Examples of such minerals are galena, iron 
pyrites, molyb-denite, bornite, chalcopyrite, car¬ 
borundum, silicon, zincite, and ceruscite. The first 
three are respectively lead sulphide, iron sul¬ 
phide and molybdenum sulphide. Bornite and 
chalcopyrite are combinations of the sulphides of 
copper and iron. Carborundum is silicon carbide, 
formed in the electric furnace. The fused metal¬ 
lic silicon commonly used is also an electric fur¬ 
nace product. Zincite is a natural red oxide of 
zinc. 

Probably the three most widely used crystals 
are galena, silicon and iron pyrites. Sensitive 
specimens of iron pyrites are more difficult to find 
than sensitive galena, but they usually retain their 
sensitiveness for a longer time than galena. 


RADIO RECEPTION 111 

These sensitive pyrites detectors are often sold 
under the trade name of “Ferron,” The detector 
sold under the name of “Perikon” consists of 
a bornite point in contact with a mass of zincite. 

Fig. 25 shows a typical crystal detector. This 
particular sample being of silicon with an anti- 



Fig. 25. Typical crystal detector. 


mony contact point. Another excellent crystal is 
ceruscite and is sold under that name. 

In order to act as a detector for radio signals a 
crystal contact should either allow more current 
to flow when a given voltage is applied in one 
direction than when it is applied in the opposite 
direction, or its conductivity should vary as dif¬ 
ferent voltages in the same direction are applied. 
Practically all detectors formed by contact of two 


























































112 


EADIO 


dissimilar substances possess both of these prop¬ 
erties, at least to a slight extent. 

To make use of the latter property, a battery is 
required in series with the crystal, as explained 
below. Some crystals, such as galena, silicon, 
ceruscite and iron pyrites give about as good re¬ 
sults as simple rectifiers as when the battery is 
used, and as a matter of fact, in common practice 
no battery is employed with them, thus making 
the apparatus more simplified and effecting 
economy. 

In order to make use of the second property, 
a local or **booster’’ battery is inserted in series 
with the crystal. Generally a small battery of 2 to 
4 volts, controlled by a potentiometer is employed. 

Telephones .—The distinctive features of 
telephone receivers for radio work are lightness of 
the moving parts and the employment of a great 
many turns of wire around the magnet poles. The 
lightness of the moving parts enables them to fol¬ 
low and respond to rapid pulsations of current. 
The large number of turns of wire causes a rela¬ 
tively large magnetic field to be produced by a 
feeble current. The combined effort is to give a 
very sensitive receiving device. Inasmuch as the 
size of the wire used is always about the same 
(No. 40 copper), the amount of wire and therefore 


RADIO RECEPTION 


113 


the number of turns is usually specified indirectly 
by stating the number of ohms of resistance in the 
coils. Telephone receivers of fair sensitiveness 
for radio work have about 1000 ohms in each re¬ 
ceiver (measured in direct current), while the 
better ones usually have 1500 to 2000 ohms per 
receiver. 

The most common type, called the magnetic dia¬ 
phragm type, has a U-shaped, permanent magnet 
with soft iron poles, and a thin soft iron dia¬ 
phragm very close to the poles, so that it vibrates 
when the attraction is rapidly varied, producing 
sounds to correspond with the frequency of the 
pulsations of current. 

The impedance of a telephone receiver to alter¬ 
nating current increases rapidly with frequency, 
and at radio frequency is so great as to permit 
no passage of current. By the use of detectors, 
however, the current that passes in the telephone 
consists of a series of pulses of audio frequency, 
usually from 500 to 1200 pulses or vibrations per 
second. A typical telephone receiver having a 
direct current impedance (resistance) of 2000 
ohms was found at 400 cycles per second to have 
an impedance of 2900 ohms, and at 800 cycles per 
second an impedance of 3900, rising to 4400 ohms 
at 1000 cycles per second. This is an excellent 


114 


RADIO 


illustration of the ratio of the frequency to the 
resistance of telephone receivers. 

Receiving Coils and Condensers *—The 
coils used in receiving apparatus are very simple 
in construction, being usually wound in a single 
layer of wire on a bakelite, pasteboard, or other 
insulating tube. The wire is usually covered with 
an insulation of silk or cotton, both solid and 
stranded wire being used. In the older type of ap¬ 
paratus, one or two sliders make contact with any 
desired turn of wire, the insulation being scraped 
off on top of the wires along a narrow path length¬ 
wise of the coil. More modem sets use no sliders, 
but have switches whose points are connected by 
tap wires to turns of wires in the coil. One 
switch takes care of single turns, and the other 
switch makes contact to groups of, say, ten turns 
each. The construction of a rough example of 
this type is explained in the chapter explaining 
how to construct a receiver, found later in this 
volume. 

Loading coils are merely large coils used to 
increase the inductance of the circuit when the 
inductance of the receiving oscillation transformer 
is not great enough to be tuned to the wave length 
received. 

Fig. 26 shows a typical receiving variable 


RADIO RECEPTION 


115 


condenser with air dielectric, which is generally 
used. The maximum capacity of these receiving 
condensers for short wave receivers, is usually 
0.0005 microfarads, adjustable to a minimum of 



Fig. 26 . Typical receiving condenser with air dielectric 

(insulation). 

nearly zero. A set of semi-circular metal plates 
is rotated between a corresponding set of fixed 
plates, forming alternate layers of air dielectric 
(insulation) with adjacent conductors of opposite 
polarity. In damped wave reception the finer 









116 


KADIO 


secondary tuning is done by a variable condenser. 
In working with vacuum tubes most of the tuning 
is done with variable condensers. In the pri¬ 
mary it sometimes happens that, with undamped 
or continuous waves, the tuning must be closer 
than that afforded by single turns of the primary 
inductance coils, so a variable condenser is placed 
in parallel with the primary and used for fine 
tuning. 

Receiving Tuners .—Having discussed the 
principal units composing a receiver or tuner, we 
shall now turn our attention to the various types 
of tuners and their circuits. 

The fundamental principle of the reception of 
signals is that of resonance, which has been dis¬ 
cussed fully in the portion of this work devoted 
to transmitters. If the receiving circuits are 
tuned to oscillate at the same natural frequency 
as the incoming waves, these waves, though ex¬ 
tremely feeble, will after a few impulses, build up 
comparatively big oscillations in the circuits. 
In reality, then, for the reception of signals, all 
that is needed is an antenna circuit tuned to the 
same wave length as that of the transmitting sta¬ 
tion, and an instrument capable of evidencing the 
current which flows in the antenna connecting 
wire. 


RADIO RECEPTION 


117 


In Fig. 27 is shown the simplest connection for 
the reception of signals with a telephone receiver. 
It is suitable only for damped waves, and also 
will receive only waves from a transmitting sta¬ 
tion that correspond to its own, or nearly its own 
natural period. At D is shown the rectifier, com¬ 
monly called a ‘ 6 detector/’ although really, it 




Fig. 27. Simplest form of receiving apparatus. 

detects nothing and merely alters the waves, so 
that the telephones may receive them. It must be 
remembered that the waves received are of radio 
frequency, which are inaudible to the human ear. 
The upper limit of audio frequency for the human 
hearing is about 15,000 sound waves per second, 
so that even if the telephone receiver diaphragm 
could, without the detector (rectifier) follow the 
radio frequency, the ear would not hear the sig- 



118 


RADIO 


nals; what the detector does is rectify the radio 
high frequency current, that is, allow but one 
alternation to pass through it, and lopping off, 
so as to speak, the other alternation of the opposite 
direction, thus reducing the alternating to direct 
current and permitting audible signals to be 
heard in the telephones. In the above circuit it 
is true that the presence of the detector and tele¬ 
phones offers high resistance in the antenna cir- 



Fig. 28. Simplest form of tuned receiving apparatus. 

cuit and renders it not very selective, so that it 
will respond to a wide range of wave lengths. 
Tuning to resonance is made possible if a tuning 
coil is introduced into the circuit, in series with 
the antenna, such as L in Fig. 28, to vary the 
inductance of the circuit and hence the wave 
lengths. 






RADIO RECEPTION 


119 


It is well to observe how simple is the apparatus 
actually needed for reception, contrary to what 
the uninitiated person supposes. Three pieces 
of apparatus, telephone receiver, dectector (rec¬ 
tifier), and tuning coil will effectively receive 
damped wave signals. The main disadvantage of 
the circuit shown above is not being able to tune 



Fig. 29. Simple coupled receiving set. 

out stations that one does not wish to hear. Also 
the amplitude of the oscillations is much dimin¬ 
ished by the high resistance of the detector and 
telephones. The principal resistance is that of 
the detector. 

To avoid the difficulties attendant upon the 
presence of the detector in the antenna circuit, 
it is customary to place the detector in a separate 
circuit coupled to the antenna; or in other words, 





120 


RADIO 


that the detecting instruments are placed in shunt 
to the tuning coil. For instance, Fig. 29 is an 
improvement and requires no more apparatus 
than that previously described, except that the 
tuning coil has two adjustable connections in¬ 
stead of one. Oscillations now take place freely 
between antenna and ground. Two telephone 
receivers are shown, connected in series, one for 
each ear. 

9 

A further improvement, as regards selectivity. 



Fig. 30. Direct coupled receiving set. 

that is, elimination of undesirable signals, is 
shown in Fig. 30 s , where a variable condenser has 
been added, C 2 . This is called the direct coupled 
connection. The antenna circuit is called the pri¬ 
mary or open circuit and consists of the induc¬ 
tance and capacitance of that circuit. The 










RADIO RECEPTION 


121 


secondary m L 2 and C 2, known as tlie closed 
circuit. In the same manner in which the trans¬ 
mitting antenna circuit is a good radiator of 
power, so is the receiving antenna a good ab¬ 
sorber. It is tuned to resonance with the incom¬ 
ing wave by adjustment of the inductance Li. 
The power is given over magnetically to the 
secondary, which is tuned to resonance by adjust- 




Fig. 31. Inductively coupled receiving circuit. 

ments to L 2 and C 2. Comparatively large oscil¬ 
lations result in the secondary, producing voltages 
across the condenser which are detected by the 
crystal and telephone, and which are not in either 
oscillating circuit, but shunted across the con¬ 
denser of the secondary. The oscillations are not 
damped thereby and sharp tuning is obtained. 















122 


EADIO 


Inductively Coupled Tuners*— Hitherto, 

we have dealt with the simplest circuits possible 
for receiving damped or spark radio signals, cir¬ 
cuits employing the least amount of apparatus 
and fewest adjustments. In Fig. 31 is shown an 
inductively coupled receiving set, which may be 
said to be the standard set of modern practice, 
and the one upon which all later changes are 
based. A fixed condenser (F.C.) of about 0.005 
microfarads is shunted around the telephone and 
this increases the strength of the signals. Its 
action is explained as follows: Suppose the prin¬ 
cipal current flows downward through the detec¬ 
tor (D) and telephone (T). While the current 
flows, the fixed condenser (F.C.) is charged with 
top plate positive. When the reversal of the 
radio oscillations comes, the current through de¬ 
tector and telephones ceases. Then the condenser 
discharges down through the telephones and tends 
to maintain the current till the next oscillation 
downward through the instruments. In this way, 
the gaps between the successive pulsations of 
rectified current are filled in, and the cumulative 
effect of a wave group is strengthened. In prac¬ 
tice the telephone cord, containing as it does two 
conductors separated by rubber, cotton and silk 
dielectric, forms a condenser which in many cases 


RADIO RECEPTION 123 

is sufficient so that an added fixed condenser gives 
no improvement. 

The connection in this set is similar in its action 
with the direct coupled arrangement above de-« 
scribed. In either case, on account of the coupling 
between primary and secondary coils, there are 
reactions of each coil upon the other, with conse^ 
quent double oscillations when the coils are near 




Fig. 32. Receiving circuit for both long and short 
waves, showing loading inductance and short wave con¬ 
denser. 

together. It is found, however, that if the resist¬ 
ance of the circuits is low, by varying the coup¬ 
ling, extremely sharp tuning is possible. The 


















124 


EADIO 


antenna is tuned to incoming waves, by changes 
of the inductance L i. If very sharp tuning is 
desired, a variable condenser is shunted around 
Li, and tine adjustments are made therewith. 
The secondary is tuned to the primary, the opera¬ 
tions of tuning being done alternately until the 
telephone gives the best response. In the sec¬ 
ondary the coarser tuning is done by changes of 
the inductance L 2 , and the finer tuning with the 
variable condenser C 2 . 

For receiving a longer wave in the primary cir¬ 
cuit than is possible by using all of the inductance 
L 2 , a series inductance L 3 called a loading coil is 
added. This is shown in Fig. 32. Also, a variable 
condenser may be connected as shown at C 3 to 
increase the wave length and afford fine tuning. 
The secondary may also be provided with an extra 
inductance in series with L 2 if needed. For re¬ 
ceiving short waves on a large antenna, series con¬ 
denser C 4 is inserted in the ground wire. It is 
short circuited when not in use. 

In the set described above, a crystal detector or 
rectifier is used as the detector. The principal 
disadvantage of this type of detector is that it 
cannot be depended upon to stay in adjustment. 
Much time would be spent and annoyance caused 
if the operator had to search for incoming sig- 


RADIO RECEPTION 125 

nals. To obviate this trouble, auxiliary apparatus 
known as a “ buzzer ’ 9 is incorporated into the set. 
This arrangement is shown in Fig. 33. By setting 
the buzzer in action, its notes are heard in the 



Fig. 33. Inductively coupled set with buzzer testing 

circuit. 

telephones, and by careful adjustment of the de¬ 
tector, when the loudest buzzer signals are heard 
so will the loudest response be heard from incom¬ 
ing radio signals. This buzzer thus enables one at 
all times to rapidly ascertain whether the detector 
is functioning. 

Having dealt with receivers and circuits em¬ 
ploying as a detecting device crystal rectifiers, we 
























126 


RADIO 


can turn to circuits utilizing vacuum tubes. 
These are rapidly replacing in modern apparatus 
the types we have just discussed. 

It will be necessary, however, before entering 
into the receiving circuits using vacuum tubes to 
discuss as briefly as possible, the theory of 
vacuum tubes, or as it is known, the “electron 
theory. ’ 9 This will present a clearer understand¬ 
ing of their value in the various uses in which they 
are employed. 










J 




* 










Fig. 35. Rear view of standard receiving apparatus 














CHAPTER VII 


VACUUM TUBES IN RADIO 

The introduction of vacuum tubes, also known 
as audions, audiotrons, vacuum valves and numer¬ 
ous other technical and trade names, resulted in 
remarkably great advances in radio communica¬ 
tion. Such tubes may be used for many purposes, 
to generate, to modulate radio oscillations, to de¬ 
tect or rectify, as well as to amplify radio signals, 
and they are now used in all types of modern 
equipment. The further development of the tube 
is rapidly progressing and new applications of 
its use develop so rapidly that one engaged in 
radio work must be an assiduous reader to keep 
in touch with these new developments. There¬ 
fore, it is of the utmost importance that the prin¬ 
ciples underlying the use of vacuum tubes and 
their operation under the widely different condi¬ 
tions met in actual radio practice, be given care-' 
ful study. 

If two wires are connected to a battery, one to 
each terminal, the other ends may be brought very 

close together in air, yet so long as they do not 

127 


128 


RADIO 


touch, no current flows between them. The two 
ends may be enclosed in a bulb like an ordinary 
incandescent lamp, and the air pumped out, leav¬ 
ing a vacuum, and still as long as the ends are 
separated, no current flows. A common experi¬ 
ence will illustrate this. When the filament of 
an electric lamp breaks, the current stops and 
the light goes out. But if one of the two wire ends 
mentioned above, is heated to a bright red, or 
hotter, it is an interesting fact that a current 
can be made to flow across the apparently empty 
space between them. 

Call the two ends of wire the “electrodes” of 
the tube. The current between the hot and cold 
electrode is made possible by the electrons given 
off by the hot electrode and is a large enough cur¬ 
rent to be measured by a sensitive instrument and 
to have highly important uses in radio com¬ 
munication, as will be shown in the succeeding 
pages. 

The Ttvo*Electrode Vacuum Tuhe .— 

The question will perhaps arise as to how a single 
electrode can be heated when it is inside of a glass 
bulb. That is simply done by shaping it into a 
loop and both ends brought through the base of 
the bulb, in exactly the same manner that the fila¬ 
ment of an incandescent lamp is used. These ends 


VACUUM TUBES IN RADIO 


129 


are connected to a battery of a few cells, generally 
giving a voltage of about six volts. The current 
from this battery heats the loop in a similar man¬ 
ner as the filament of the above mentioned electric 
lamp. Thus the hot filament becomes one of the 
electrodes. For the other electrode a little plate 
of metal is used. A bulb containing a hot and a 
cold electrode as thus described forms a “two 
electrode vacuum tube” and was originally de¬ 
signed by Professor J. A. Fleming. 

The action of these tubes depends upon the 
fact that when a metal is heated in a vacuum it 
gives off electrons into surrounding space. A 
study of these electrons is important, the reason 
for this is that all matter contains them. Matter 
of all kinds is made up of atoms, which are ex¬ 
tremely small portions of matter (a drop of water 
contains billions of them). These atoms in turn 
contain electrons which consist of negative elec¬ 
tricity. The electrons are all alike and are much 
smaller than the atoms. Besides containing elec¬ 
trons, each atom also contains a certain amount 
of positive electricity. Normally the positive and 
negative electricity are just about equal. How¬ 
ever, some of the electrons are not held so firmly 
to the atom, but what they can escape if the atom 
is violently knocked or jarred. Therefore, when 


130 


EADIO 


an electron, negatively charged, leaves an atom, 
there is then less negative electricity than positive 
in the atom; in this condition the atom is said to 
be positively charged. The atoms in matter are 
constantly in motion, and when they strike against 
one another electrons are jarred from an atom. 
This electron then moves about freely between the 
atoms. Heat has an effect upon this process. 
The higher the temperature, the faster the atoms 
move and the more electrons given off. It is this 
action of electrons that is made use of in the 
vacuum tube. 

As the electrons have a negative charge, the 
charge remaining on the metal is positive, there¬ 
fore few of the electrons go very far, hut are 
attracted hack to the metal, so that there is a 
kind of balance established between the outgoing 
and the returning electrons. Now, suppose a 
battery is connected between the two electrodes, 
that is, between the hot filament and the plate. 
This battery is so connected as to make the plate 
positive with respect to the filament. The elec¬ 
trons, being of negative electricity, would be at¬ 
tracted by the plate and retained, returning no 
more to the filament. Thus the battery causes a 
continuous flow of negative electrons from the 
filament to the plate. In other words, a current 


VACUUM TUBES IN RADIO 131 

of negative electricity is flowing in space between 
the two electrodes of the tube. 

The current ceases when the filament is cold, 
because no electrons are then escaping from the 
metal. No current will flow if the battery is 
wrongly connected, since, when the plate is nega¬ 
tive with respect to the filament, the negative 
charge of the plate will repel the electrons back 
into the filament. 

The distinction between direction of current 
and direction of electron flow must be carefully 
noted. It happens that for a great many years 
the direction from the positive toward the nega¬ 
tive terminal has been arbitrarily called the direc¬ 
tion of the current. It is now found that these 
little electrons travel from the negative toward 
the positive electrode. The direction of current 
and the direction of the motion of the electrons 
are therefore opposite. 

Ionization .—The foregoing explanation of 
the action of the flow of current between filament 
and plate, commonly called the 4 4 plate current, ’ ’ in 
a vacuum tube applies to the case where the 
vacuum of the bulb is very complete. If there is 
more than the merest trace of gas remaining in 
the tube, the operation is more complicated, and 
a larger current will usually flow with the same 


132 BADIO 

applied voltage. This is accounted for in the fol¬ 
lowing manner: 

In a rarefied gas, some of the electrons are con¬ 
stituent parts of atoms and some are free. These 
free electrons move about with great velocity, and 
if one of them strikes an atom it may dislodge 
another electron from the atom. Under the action 
of the emf. between plate and filament, the 
newly freed electron will acquire velocity in one 
direction, which will be similar to that of the col¬ 
liding electron and the positively charged re¬ 
mainder of the atom will move in the opposite 
direction. Thus both of the parts of the disrupted 
atom become carriers of electricity and contribute 
to the flow of current through the gas. This 
action of a colliding electron upon an atom is 
called “ionization by collision,” and on account 
of it relatively large plate currents are obtained 
in vacuum tubes having a poor vacuum. The 
earlier tubes were of this sort, but modern tubes, 
as a rule, are made with a better vacua than form¬ 
erly, so that ionization by collision is responsible 
for but a small part of the current flow. However, 
tubes such as those above described are often in 
demand in radio practice for certain uses and are 
alluded to as “soft tubes.” 

In the earlier use of vacuum tubes it would seem 


133 


VACUUM TUBES IN BADIO 

an advantage to have ionization by collision, be¬ 
cause a larger plate current can be obtained, but 
there are two difficulties which have proved so 
great that tubes are now usually made to have 
only a pure electron flow. One of these difficulties 
is a rapid deterioration of the filament when a 
large plate current flow r s. The positively charged 
parts of the atoms are driven violently against 
the negatively charged filament and since they 
are much more massive than electrons, this bom¬ 
bardment, so to speak, actually seems to wear 
away the surface of the filament. Another dis¬ 
advantage of tubes of poor vacuum is that too 
large a battery voltage may cause a “blue glow” 
discharge. This action applies more particularly 
to the efficiency of “three element tube,” de¬ 
scribed below. 

The tube described above was the first used in 
radio practice and after its inventor is called the 
‘ < Fleming valve. ’ ’ The Fleming valve was origin¬ 
ally used as a detector, but has been replaced by 
the three-element tube discussed below because 
the latter has proved so much more sensitive, and 
as previously described, can be utilized for a va¬ 
riety of purposes. 

However, before proceeding to the modern 
vacuum tube, it is well to consider that types of 


134 


RADIO 


two-electrode tubes are most useful in another 
field of electrical work. One type, known as the 
“Kenetron,” developed by the General Electric 
Company, has a higher vacuum than the Flem¬ 
ing valve and is made in larger dimensions. It is 
used as a rectifier of currents of high voltage, but 
low frequency. It changes alternating current 
into a pulsating current all in one direction. 
Small currents, well below one ampere, are recti¬ 
fied by these tubes, and power up to several kilo¬ 
watts can be handled even if the applied voltage 
exceeds 25,000. 

Another type, known as a “Tungar rectifier” 
is utilized for charging storage batteries from a 
110 volt alternating current circuit. This type 
contains rarefied argon gas and relatively large 
currents are produced mainly through ionization 
by collision, in the manner before described. 

The Three-Electrode Vacuum Tube .— 
A great improvement upon a two-electrode tube 
for radio purposes, consists in the addition of a 
third electrode or element, inside the tube in the 
form of a metallic gauze, or, as it is known, 
“grid.” This grid consists of an electrode of 
fine wires between the filament and the plate of 
the vacuum tube. This makes it possible to in¬ 
crease or decrease the current between plate and 


VACUUM TUBES IN RADIO 


135 


filament through wide limits. In order to under¬ 
stand how this result is obtained, it will be neces¬ 
sary to first consider what happens in a two- 
electrode tube having a good vacuum, when either 
the voltage of the “B” battery or the tempera¬ 
ture of the filament is varied. 

Suppose that the filament temperature is kept 
constant, then a definite number of electrons will 
be sent out per second. The number of electrons 
that travel across the tube and reach the plate per 
second determines the magnitude of the current 
through the plate circuit. The number of electrons 
that reach the plate increases as the voltage of 
the “B” battery increases. If this voltage is con¬ 
tinuously increased, a value will be reached at 
which all the electrons sent out from the filament 
will arrive at the plate, therefore we arrive at 
what is termed the “saturation” current, as no 
further increase of the electron flow can be ob¬ 
tained by increasing the voltage. 

Suppose now that the voltage of the “B” bat¬ 
tery is kept a constant value, and the filament 
temperature gradually raised by increasing the 
current from the heating battery, known also as 
the “A” battery. The number of electrons sent 
out will continue to increase as the temperature 
rises. The electric field intensity, due to the pres- 


136 


RADIO 


ence of negative electrons in the space between 
the filament and plate, may at last equal and neu¬ 
tralize that due to the positive potential of the 
plate so that there is no force acting on the elec¬ 
trons near the filament. This effect of the elec¬ 
trons in the space is called the “ space charge 
effect/’ It must not be supposed that the space 
charge effect is caused by the same electrons all 
the time. Electrons near the plate are constantly 
entering it, but new electrons emitted by the fila¬ 
ment are entering the space, so that the total 
number between filament and plate remains con¬ 
stant at a given temperature. After the tempera¬ 
ture of the filament has reached the point where 
the effect of the electrons present in the space 
between filament and plate neutralizes the effect 
of the plate voltage, any further increase of the 
filament temperature is unable to cause an in¬ 
crease in the current. The tendency of the fila¬ 
ment to emit more electrons per second because 
of the increased temperature, is offset by the 
increase in space charge effect, which would result 
if electrons were emitted more rapidly; or, to 
put it more exactly, for any extra electrons emit¬ 
ted, an equal number of those in the space are 
repelled back into the filament. 

Thus, whether the “A” battery is kept at a 


VACUUM TUBES IN RADIO 


137 


constant value and the “B” battery varied, or 
vice versa, in either case we find that the electron 
flow or plate current can only rise to certain value. 

In the three-electrode tube, by inserting a grid 
between the filament and the plate, as stated 
before, in the form of several small wires, the 
grid is placed in the path of the stream of elec¬ 
trons which constitute the plate current. When 
this grid is charged positively, the space charge 
will be neutralized, as it is of a negative char¬ 
acter and thus a greater plate current will result. 
Also, if the grid be charged negatively, the space 
charge will be increased, and a greater number of 
electrons driven back to the filament, with a les¬ 
sening of the plate current. Thus it will be seen 
that the value of the plate current can be con¬ 
trolled by means of the third element or grid in 
the vacuum tube. This control is accomplished 
in a variety of ways, depending upon the use 
for which a given set is designed, also, upon the 
characteristics of the particular vacuum tube 
used. Various tubes have a variance of charac¬ 
teristics. 

Circuits that may be utilized in the employment 
of the vacuum tube, showing various methods of 
vacuum tube control are to be found in the fol¬ 
lowing pages. 


138 


RADIO 


A.s a Damped Detector . —We shall first 
take a simple detector circuit and an explanation 
of its action. In order to understand how a 
vacuum tube acts when used as a detector, con¬ 
sider the circuit shown in Fig. 36. Suppose the 



mszm 

Fig. 36. Connections for using vacuum tube as a simple 

detector. 

receiving antenna picks up a signal. Oscillations 
in the tuned circuit L C, are set up, because L is 
inductively coupled to the antenna circuit. The 
radio frequency alternating voltage between the 
terminals of L is impressed between the filament 
and grid, and brings about changes in the plate 
circuit. On the average the plate current is in- 























VACUUM TUBES IN RADIO 


139 


creased while the signal is passing. The fre¬ 
quency of the wave trains should be within the 
range of audible sound, preferably between 300 
and 2,000, because the telephone inductance 
smooths out each train of high frequency oscilla¬ 
tions into a single pulse and the pulse frequency 
must, therefore, be within the audible range in 
order that signals may be heard. 

In some cases it may be necessary to use a 
11 C ’ 9 battery between points f and g in Fig. 36 in 
order to bring the plate current to a correct value. 
This, however, does not change the action; the 
variations of the plate current are brought about 
by the alternating emf. between the terminals of 
coil L just the same as when the C battery is 
absent. 

If the grid battery voltage is adjusted so that 
the plate current has a value near the upper bend 
of the plate current-grid voltage curve instead of 
the lower bend, the action will be essentially the 
same, but the effect of the arrival of a wave train 
will be to decrease momentarily the plate current 
instead of to increase it. As before, there will be 
fluctuations of the plate current keeping time with 
the arrival of train waves, and a sound in the tele¬ 
phone of a pitch corresponding to the number of 
wave trains per second. 


140 


RADIO 


Care must be taken in the use of receiving tubes 
that the B battery voltage is never high enough 
to cause a visible “blue glow.” The tube becomes 
very erratic in behavior when in this condition, 
and is very uncertain and not sensitive as a re- 



Fig. 37. Vacuum tube as detector of undamped waves. 

Condenser in grid circuit. 

ceiver. This is because the plate current becomes 
so large that it is unaffected by variations of the 
grid voltage. Furthermore, the tube gets hot and 
its safety is endangered by the blue glow dis¬ 
charge. 

If the circuit shown in Fig. 37 is used, having 

























VACUUM TUBES IN RADIO 


141 



Fig. 38. Reception with grid condenser in circuit. 
(1) Incoming oscillations, (2) grid current, (3) grid 
potential, (4) plate current, (5) current in phones. 






















142 


RADIO 


a condenser in series with the grid, the action of 
the tube as a detector is different. When the grid 
voltage is the same as that of the filament and 
there are no oscillations, the grid current is zero; 
that is, no electrons are passing from the fila¬ 
ment to the grid. Now suppose that a series of 
wave trains falls upon the antenna of Fig. 37, as 
shown in (1) of Fig. 38. If the circuit LC. is 
tuned to the same wave length as the antenna cir¬ 
cuit, oscillations will be set up in it, and similar 
voltage oscillations will be communicated to the 
grid by means of the stopping condenser C 2 (A 
suitable capacity value for this condenser would 
be 0.0001 mfd). Each time the grid becomes posi¬ 
tive, electrons will flow to it, but during the nega¬ 
tive half of each oscillation no appreciable grid 
current will flow. This is shown in curve (2) of 
Fig. 38. Thus during each wave train the grid 
will continue gaining negative charge and its aver¬ 
age potential will fall as shown in (3) of the same 
figure. This negative charge on the grid opposes 
the flow of electrons from filament to plate, 
causing on the whole, a decrease in the plate cur¬ 
rent. At the end of each wave train this charge 
leaks off through either the condenser or the walls 
of the tube (or both) and the plate current rises 
again to its normal value as shown in (4) of the 



VACUUM TUBES IN RADIO 


143 


same figure. This should happen before the next 
wave train comes along, but sometimes the leak is 
not fast enough for the discharge to take place. 
In this case a better result is secured if a resist- 



Fig. 39. Vacuum tube as an amplifier. 

ance of a megohm or so is shunted across the con¬ 
denser. Such a resistance is called a grid leak. 

The telephone diaphragm cannot vibrate at 
radio frequency, but the high inductance of its 
coils smooths out the plate current variations into 
some such form as shown in (5) in Fig. 38. Thus 
as in the case of the circuit in Fig. 37, the note 
heard in the telephone corresponds in pitch with 
the frequency of the wave trains. To receive un- 




















144 


EADIO 


damped waves which are not divided up into 
groups of audible frequency, vacuum tubes may 
be used in special ways called the heterodyne and 
autodyne methods, which are explained later in 
this chapter. 

The Vacuum Tube As An Amplifier .— 

If, as in Fig. 39, a source of alternating emf. 




Fig. 40. Variations of plate current with grid voltage. 


were interposed between the filament and grid of 
an audion the potential of grid with respect to the 
filament would alternate in accordance with the 
alternations of the generator. These variations 
of the grid potential produce changes in the plate 





VACUUM TUBES IN RADIO 


145 


current corresponding to the plate characteristic. 
If the mean potential of the grid and the ampli¬ 
tude of its alternations are such that the plate 
current is always in that portion of its charac¬ 
teristic where it is a straight line, then the alter¬ 
nations of the grid potential will be exactly dupli¬ 
cated in the variations of the plate current and 
the latter will be in phase with the former, at least 
in a high vacuum tube. Thus, if (a) of Fig. 40 
represents the alternating potential of the grid, 
then (b) would represent the fluctuations of the 
plate current. For a given amplitude in (a) the 
amplitude of the alternating component in (b) 
will depend upon the steepness of the plate char¬ 
acteristic, increasing with increasing slope. The 
alternator in the grid lead supplies only the very 
small grid filament current, thus the power drawn 
from it is extremely small. The power repre¬ 
sented by the alternating component of the plate 
current is, however, considerable; thus there is 
very large power amplification. This larger 
source of power might be utilized by inserting the 
primary P of a transformer in the plate circuit, 
as in Fig. 39, in which case the alternating com¬ 
ponent above would be present in the secondary 
S. This illustrates the principle of a vacuum tube 
as a relay. The voltage in S might again be in- 


146 


BADIO 


serted in the grid lead of a second vacuum tube 
and with proper design a further amplification 
obtained in the second tube. This may be carried 



5 P 

Fig. 41. Use of vacuum tubes as a regenerative amplifier 

(feed back circuit). 


through further stages and illustrates the prin¬ 
ciple of multiple amplification. 

Regenerative Amplification .—It has 
been shown by Mr. E. H. Armstrong, that amplifi¬ 
cation similar to that obtained with several stages 
may be secured with a single tube. Instead of 
feeding the voltage of the secondary coil S into the 
grid circuit of a second tube it is fed back into the 

























VACUUM TUBES IN RADIO 147 

grid circuit of the same tube so as to increase 
the voltage operating upon the grid. This results 
in an increased amplitude of the plate current 
alternations, which likewise being fed back into 



Fig. 42. Circuit for use of vacuum tube for reception of 

undamped waves. 

the grid circuit increases the voltage operating 
upon the grid, etc. 

One form of the so-called feed-back circuit for 
rectifying and amplifying damped oscillations is 
shown in Fig. 41. The operation of the circuit, 































148 


RADIO 


used as a receiving device, is the same as that de¬ 
scribed above for the case of a condenser in the 
grid leak. The condenser C 2 is merely to pro¬ 
vide a path of low impedance across the phones 
for high frequency oscillations. The coils P and 
S constitute the feed back by means of which the 
oscillations in the tuned circuit are reinforced. 
The mutual inductance between S and P must be 
of the proper sign, so that the emf. feed back 
aids the oscillations instead of opposing them. 

Reception of Undamped Waves .—In 
Fig. 42 is shown the connections for the reception 
of undamped waves. This circuit was used by 
Dr. Lee DeForrest, the inventor of the three elec¬ 
trode vacuum tube, which he called an audion. He 
termed this circuit the “ultraudion.” The oscilla¬ 
tory circuit is connected between the grid and the 
plate with a condenser in the grid lead. The vari¬ 
able condenser C 2 shunted across the plate bat¬ 
tery and phones is important in the production 
of oscillations; in general, its value cannot be in¬ 
creased beyond a certain point without stopping 
the oscillations. 

By this beat method high sensitiveness and 
selectivity are attained in receiving. Interference 
is minimized because even slight differences in 
frequency of the waves from other sources result 


VACUUM TUBES IN RADIO 149 

in notes either of different pitch or completely 
inaudible. 

Heterodyne and Antodyne Recep¬ 
tion .—If two tuning forks mounted on resonance 
boxes, one vibrating 256 and the other 260 times 
per second are sounding together, a listener a 
short distance away will hear a sound alternately 
swelling out and dying away four times per sec¬ 
ond. These tone variations are called ‘ 4 beats.’’ 
Similarly if two sources of undamped electrical 
oscillations act simultaneously upon the same cir¬ 
cuit, one of a frequency of 500,000 and the other of 
501,000, the amplitude of the combined oscillation 
will successively rise to a maximum and fall to a 
minimum 1,000 times per second. If rectified by a 
vacuum tube (or a crystal) their variations will 
produce an audible note of frequency 1,000 per 
second in a suitable telephone receiver. If one 
of the two oscillations is the received signal in the 
antenna and the other is generated by a circuit in 
the receiving station, we have “ heterodyne ” or 
“beat reception.’* In the receiving telephone a 
musical note is heard, the pitch of which is readily 
varied by slight variation of tuning of the local 
generating circuit. 

If a regenerative circuit similar to that of Fig. 
41 is used (L being coupled to the antenna), the 


150 


BADIO 


same tube may be used as a detector and as a 
generator of local oscillations. This is called the 
“autodyne” reception. The procedure is to tune 
the antenna circuit to the incoming signals and 
adjust the local oscillating circuit so that it is 
slightly out of tune with these incoming signals. 
Thus beats of audible frequency are produced. 

By these methods of reception very faint sig¬ 
nals can be received. Also interference from other 
stations is reduced to a minimum, because a slight 
difference in frequency of the interfering signal 
would give a note of an entirely different pitch, 
or even inaudible. For instance, if the local oscil¬ 
lation had a frequency of 500,000 the received 
oscillation 501,000 and the interfering oscillation 
502,000, the interfering note would have a fre¬ 
quency of 2,000, or be a whole octave higher in 
pitch than the received note. If the interfering 
source had a frequency of 530,000, its beat tone 
would be so high as to be entirely inaudible. 


CHAPTER Vin 


RADIO TELEPHONY 

The principles of radio telephony are the same 
as those of radio telegraphy by undamped waves 
except that the sending key is replaced by appar¬ 
atus which varies the sending current in accord¬ 
ance with the sound waves produced by the voice. 
A wave of radio frequency is sent out by the 
antenna, the intensity of which varies with the 
frequency of the voice sound waves. The sound 
waves have a frequency much lower than the radio 



Fig. 43. Voice modulations of antenna oscillations. 
A, fluctuations in grid voltage. B, varying amplitude 
of oscillations. 


frequency, so that each sound wave lasts over a 
considerable number of radio alternations, as in 
the lower curve of Fig. 43. The radio wave is 

151 













152 


RADIO 


thus transmitted in pulses, and is received on any 
ordinary apparatus used for receiving damped 



Fig. 44. Circuit for vacuum tubes as a generator of 

undamped waves. 

wave radio telegraph signals, such as previously 
described. 

The power involved in the sound waves gen¬ 
erated in ordinary speech is relatively very small, 
yet this must be made to control a kilowatt or 
more of radio frequency power in long distance 
radio telephony. The effect of the sound waves 




















KADIO TELEPHONY 


153 


must therefore be amplified. The way in which 
the audio frequency is made to control the ampli¬ 
tude of the radio oscillation will now be explained. 
Suppose a generator of radio oscillations is 





c 



Pig. 45. Control of antenna current in radio telephony 
by vacuum tube modulator. 

placed in series with the antenna, as in Fig. 44. 
Various types of arc, quenched spark, timed 
spark, high frequency alternators, and vacuum 
tube oscillators have all been used as sources with 
more or less success. The controlling device is 
usually the combination of a telephone transmit¬ 
ter with an arrangement of vacuum tube circuits, 
as shown in Fig. 45. The plate circuit of the 
vacuum tube is inductively coupled to the antenna 
by the coil L. The grid of the tube is kept at a 




















154 


RADIO 


negative voltage by battery C. The current 
through the antenna coil induces potential differ^ 
ences between filament and plate, but this pro¬ 
duces only very slight changes in plate current on 
account of the large negative voltage of the grid. 
Now suppose voltage variations of audio fre¬ 
quency are impressed on the grid by means of 
the telephone transmitter T and the transformer 
Tr. As the grid becomes less negative, or even 
somewhat positive, the rectified plate current in¬ 
creases, absorbing power from the antenna and 
diminishing the amplitude of the antenna oscilla¬ 
tions. The high frequency oscillations in the 
antenna therefore show variations in amplitude 
which keep time with the audio frequency varia¬ 
tions of voltage in the grid circuit, diminution of 
antenna current corresponding with increasing 
positive potential of grid. These variations are 
illustrated in Fig. 43. In the upper part of the 
figure the fluctuations of grid voltage due to the 
telephone transmitter appear; in the lower part 
of the figure are shown the resulting variations in 
the amplitude of the high frequency oscillations in 
the radiating antenna. 

The audio frequency variations of amplitude in 
the radio frequency wave will be reproduced in 
the antenna of the receiving station, and these 



RADIO TELEPHONY 


155 


will be rectified in the receiving circuit, giving 
in the telephone receivers audio frequency varia¬ 
tions of current, corresponding in frequency and 
wave form to the boundary of the curve in the 
lower part of Fig. 43 (as shown on dotted line). 


CHAPTER IX 


ANTENNAE 

The antenna is used in radio communication 
for two purposes: (1) to radiate electric waves, 
and (2) to absorb or detect the electric waves 
which come to it. An antenna consists essentially 
of one or more wires, suspended at some eleva¬ 
tion above the earth. When electric waves reach 
an antenna, they set up an alternating emf. be¬ 
tween the wires and the ground. As a result of 
this electromotive force (emf.), an alternating 
current will flow in the antenna wires. The energy 
of the current is absorbed from the passing wave, 
just as some of the energy of a water wave, is 
used up in causing vibrations in a slender reed 
which stands in its way. 

A receiving antenna needs to be large, in order 
to gather in enough energy from the passing 
waves to effect the receiving apparatus. Likewise 
a transmitting antenna should be as large as prac¬ 
ticable in order to send waves to a greater dis¬ 
tance. However, several conditions govern the 

156 


ANTENNAE 


157 


size of the transmitting aerial, just, for instance, 
as the size of the heat radiators in an apartment 
are governed by the amount of heat available to 
be radiated. The same antenna may be used for 
both receiving and transmitting, in such cases a 
change-over or antenna switch is provided in the 
set to change from reception to transmission, and 
vice versa. An antenna used for receiving only, 
may, however, be made simpler than one which 
is also required for sending purposes, as it is 
obvious, with the absence of the high potential 
emitted by a transmitter, that the insulation need 
not be so heavy. 

In practice, stranded wire is used for an 
antenna. High frequency currents with a high 
potential travel over the surface of a wire, there¬ 
fore, a stranded wire offers a large surface. It 
has another advantage, in the event of a strain 
being placed upon the antenna, one or more of the 
strands may part, but the remainder will keep 
the antenna in commission. 

As discussed in the chapter dealing with con¬ 
ductors, copper is the best conductor, but for sev¬ 
eral reasons, it has been discovered that pure cop¬ 
per is not as practicable as some alloys, therefore, 
in almost universal radio practice, silicon bronze 
or phospher-bronze are used. The standard 


158 


RADIO 


gauges are usually 7-22 or 7-19. In other words 
seven strands of number 22 or number 19 wire. 

All joints in an antenna must be soldered, or 
a suitable patent joint used, such as that called 
a 4 ‘ MacIntyre ’ 9 splice. If joints are soldered, 
care must be taken that too much heat is not em¬ 
ployed, otherwise the wiring at the joint becomes 
tempered and very brittle and is liable to break 
when any strain or jar is met with. 

The insulation of an antenna is of the utmost 
importance, especially in damp foggy climates. 
For damped apparatus using moderate power, an 
insulator known as “Electrose” is very suitable 
and is manufactured in a very large variety which 
meets all demands. For undamped or continuous 
wave radio, and for high potentials, porcelain 
is possibly the best insulator; these are also made 
in a great variety and can be readily 
obtained for any purpose. Not only should 
the actual antenna receive great care in its 
insulation, but the guy wires of masts or towers 
should also be insulated with strain insulators. 
If they are lengthy several strain insulators 
should be employed, inserted in series with the 
guy at suitable intervals. 

Types of Antennae .—Early in the history 
of radio, Marconi demonstrated that radiation 


ANTENNAE 


159 


from an antenna was directional in its effect, ac¬ 
cording to tlie shape of the aerial employed. It 
was this discovery which led in later years to the 
wonderful success of the direction finder or radio 
compass. 

It is well known, that a single vertical wire is, 
for its size the best radiator, but it has to be made 
so extremely long in order to obtain sufficient 
capacity that it is not a practical antenna for long 
wave or long distance work. Antenna of dif¬ 
ferent numbers of horizontal or inclined wires are 
therefore used, and are very practicable and 
radiate very well. It must be remembered that 
an antenna is merely a large condenser and may 
have various shapes consistent with this condi¬ 
tion, although some forms will radiate much bet¬ 
ter than others. 

Antennae that radiate more energy in one direc¬ 
tion than in the opposite, are termed “direc¬ 
tional, ’ 9 while an antenna radiating equally in all 
directions, is called “uni-directional.” 

The following types of antennae are the most 
common in practical use, and are easier to erect 
under conditions that confront the average exper¬ 
imenter. They are shown in Fig. 46. 

What may be considered as the standard form 
of antenna for ship stations, and also for low 


160 


RADIO 


powered land stations, is known as the T or in¬ 
verted L type of aerial. This is an antenna of 
horizontal wires, usually two or four in number, 



Fig. 46. Typical antennae. 


separated at equal distance on what is termed a 
spreader, and supported between two masts or 
towers. 

Whether the down leading-in wires are taken 
from the center or at the end of the horizontal 
portion determines whether the antenna is of the 
T or inverted L type. 

Another very practicable type for certain work 
is the V antenna, consisting of two sets of hori- 














































ANTENNAE 


161 


zontal wires supported by three masts or towers, 
so that the horizontal portions form an angle 
or V. 

The directional effect of an inverted L or Y 
type, is greater than a T. There is a greater 
amount of energy sent in the direction in which 
the angle of the L points than in the opposite. 
With the T type the effect is more unidirectional, 
although more energy is sent in the parallel di¬ 
rection of the horizontal wires, than at right 
angles. The resultant wave would be oval in 
shape. 

A more recent development in this field is what 
is known as the loop antenna. This consists of a 
coil frame constructed by fastening four wooden 
struts together in the form of a triangle, the apex 
of which fits into a wide slot in a center fastening, 
usually in the form of a casting. Four of these 
are provided and converge into the center cast¬ 
ing, where they are held by bolts. This pro¬ 
vides a square frame over which many coils of 
wire are wound. The two ends of the wire are 
brought in as leads. This loop is mounted on a 
shaft enabling the loop to be rotated in all di¬ 
rections, and the antenna thus cuts any lines of 
force desired. This is the type used for radio 
compasses. 


162 


BADIO 


Current and Voltage distribution .— 

When an electromotive force is introduced into 
an antenna, a charging current flows in the wires. 
If we attempt to form a picture of this process in 
the wire antenna, we must remember that every 
inch of the wire forms a little condenser, with the 
earth acting as the other plate. The antenna is 
said to have a distributed capacity. As electricity 
flows from the bottom of the antenna, some of it 
accumulates on each portion of the wire, causing 
a displacement current to earth through the di¬ 
electric. The current in the w T ire accordingly 
diminishes as the free end of the antenna is ap¬ 
proached, and becomes zero at the end. The cur¬ 
rent is evidently different at different parts of 
the antenna, being zero at the free end and a 
maximum where the antenna is connected to the 
ground. This is in marked contrast to the case 
of direct current, which always has the same 
value at every point of the current. The dif¬ 
ference here is brought about by the very high 
frequency of the currents. 

The voltage of the antenna, on the contrary, is 
zero at the grounded end and has a maximum 
value at the free end. In fact, the latter is the 
point where the most intense sparks can be drawn 
off; therefore, the insulation of the antenna from 


ANTENNAE 


163 


nearby objects and the earth must be particu¬ 
larly good at this point. 

A large capacity to earth, concentrated at any 
point of the antenna, causes a large change in the 
current at that part of the antenna. If this 
bunched capacitance is located at the top of the 
antenna, such as is the case with a flat topped an¬ 
tenna of long wires, with only a few vertical lead- 
in wires, the average current in the flat top por¬ 
tion will be large, and it increases slightly in 
strength as the charges pass down through the 
lead-in wire (picking up the changes there), 
hence, giving a large current through the receiving 
apparatus. It is a distinct advantage to have as 
large a part of the total capacity of the antenna 
as possible at the top. 

Grounds and Counterpoises . — The 

ground connections of some stations are often 
very elaborate affairs, a considerable number of 
copper plates or heavy wires, arranged radially 
from the foot of the antenna, being buried in moist 
earth. In general, the endeavor is made to in¬ 
sure a considerable area of conducting material 
in contact with the moist earth. 

As the average experimenter probably is estab¬ 
lished in a house or apartment house, such an 
arrangement is not always feasible; therefore, he 


164 


RADIO 


must cast about for the most convenient means 
of ground. If tbe building is of steel frame con¬ 
struction a connection to the steel makes a desir¬ 
able ground, care being taken to see that a good 
solid connection is made. Otherwise a connection 
to the water supply piping is the best method of 
grounding. Gas and radiator piping should be 
avoided. 

Too much emphasis cannot be laid upon the 
necessity of making the leads from the apparatus 
to the ground as short as possible, care being 
taken to have the lead with as large a surface as 
possible. For this purpose stranded flexible wire, 
or a broad strip of copper is desirable. A long 
thin wire offers high resistance, decreasing the 
received signals and decreasing the radiation of 
a transmitter. 


CHAPTER X 


DEFINITIONS 

The following are brief definitions of electrical 
terms and explanations of various instruments 
used in radio telegraphy and telephony. 

Many of these definitions are from the result of 
the work of the standardization committee of the 
Institute of Radio Engineers. 

Absorbtion —That portion of the total loss of rad¬ 
iated energy due to atmospheric conductivity. 

Ammeter —An instrument for measuring the cur¬ 
rent of electricity flowing in a circuit (See 
ampere). 

Ammeter, Hot Wire —An ammeter dependent for 
its indications upon the change in dimensions 
of an element which is heated by a current 
through it. 

Ammeter, Thermo —An instrument for measur¬ 
ing current, depending for its indications on 
the voltage generated at the terminals of a 

165 


166 


RADIO 


thermo junction heated either directly or in¬ 
directly by the current to be measured. 

Amplifier or Amplifying Relay —An instrument 
which modifies the effect of a local source of 
energy in accordance with variations of re¬ 
ceived energy; and, in general produces a 
larger indication than could be had from the 
incoming energy alone. 

Amplification, Coefficient of —The ratio of the 
useful effect obtained by the employment of 
the amplifier to the useful effect obtained 
without that instrument. 

Antenna —A system of conductors designed for 
radiating or absorbing the energy of electro¬ 
magnetic waves. 

Antenna, Directive —An antenna having the prop¬ 
erty of radiating a maximum of energy in one 
(or more) directions. 

t 

Antenna, Flat Top —An antenna having horizon¬ 
tal wires at the top covering a large area. 

Antenna, Harp —An antenna having approxi¬ 
mately vertical sections of large area and 
considerable width (This description may 
also be applied to a fan antenna). 

Antenna, Inverted L —A flat top antenna in which 


DEFINITIONS 


167 


the leading down wires are taken from one 
end of the long narrow horizontal section. 

Antenna , Loop —An antenna in which the wires 
form a closed circuit, part of which may be 
the ground. 

Antenna, Plain —An approximately vertical 
single wire. 

Antenna, T —A flat top antenna in which the hori¬ 
zontal section is long and narrow, the lead¬ 
ing down wires being taken from the center. 

Antenna, Umbrella —One whose conductors form 
the elements of a cone from the elevated apex 
of which the leading down wires are brought. 

Antenna Resistance —An effective resistance 
which is numerically equal to the ratio of 
the power in the entire antenna circuit to the 
square of the R. M. S. current at a potential 
node (generally the ground). 

Note—Antenna resistance includes: 

Radiation resistance. 

Ground resistance. 

Radiation frequency ohmic resistance of 
antenna and loading coil and shortening 
condensers. 

Equivalent resistance due to corona, eddy 
currents, and insulator leakage. 


168 RADIO 

Arc —The passage of an electric current of rela¬ 
tively high density through a gas or vapor, 
the conductivity of which is mainly due to 
the electron emission from the self-heated 
cathode. Under present practical conditions 
the phenomena takes place near atmospheric 
pressure. 

Arc Oscillator —An arc used with an oscillating 
circuit for the conversion of direct to alter¬ 
nating or pulsating current. The oscillations 
generated are classified as follows: 

Class 1. Those in which the amplitude of 
the oscillation circuit current produced 
is less than the direct current through 
the arc. 

Class 2. Those in which the amplitude of 
the oscillation circuit current is at least 
equal to the direct current, but in which 
the direction of the current through the 
arc is never reversed. 

Class 3. Those in which the amplitude of 
the initial portion of the oscillation cir¬ 
cuit current is greater than the direct 
current passing through the arc, and in 
which the direction of the current 
through the arc is periodically reversed. 


DEFINITIONS 


169 


Attenuation (Radio )—This is the decrease, with 
distance from the radiating source, of the 
amplitude of the electric and magnetic forces 
accompanying (and constituting) an electro¬ 
magnetic wave. 

Attenuation, Coefficient of (Radio )—The co¬ 
efficient which, when multiplied by the dis¬ 
tance of transmission through a uniform 
medium, gives the natural logarithm of the 
ratio of the amplitude of the electric or mag¬ 
netic forces at that distance to the initial 
value of the corresponding quantities. 

Audiblity —The ratio of the telephone current 
variation producing the received signal, to 
that producing an audible signal (An audible 
signal is one which permits the mere differen¬ 
tiation of dots and dashes). 

The measurement of audibility is an arbi¬ 
trary method for determining the relative 
loudness of telephone response in radio re¬ 
ceivers, in which it is stated that a signal 
has an audibility of given value. The de¬ 
termination of the above ratio may be made 
by the non-inductive shunt-to-telephone 
method, except that a series resistance should 
be inserted to keep the main current con- 


170 


RADIO 


stant, and that the shunt resistance should 
therefore be connected as a potentiometer. 

Brush or Corona Losses —Those due to leakage 
convection electric currents through a gase¬ 
ous medium. 

Cage Conductor —A group of parallel wires ar¬ 
ranged as the elements of a long cylinder. 

Changer, Frequency —A device delivering alter¬ 
nating current at a frequency which is some 
multiple of the frequency of the supply cur¬ 
rent. 

Changer, Wave —A transmitting device for rap¬ 
idly and positively changing the wave length. 

Characteristic, Dynamic, of a Conductor —(For a 
given frequency and between given extremes 
of impressed emf. and resultant current 
through a conductor): This is the relation 
given by the curve obtained when the im- 
presed electromotive forces are plotted as 
ordinates against the resultant currents as 
abscissas, both electromotive forces and cur¬ 
rents varying at the given frequency and be¬ 
tween the given extremes. 

Characteristic, Static of a Conductor —This is the 
relation given by the curve plotted between 
the impressed electromotive force as ordi- 


DEFINITIONS 


171 


nates and the resultant current through the 
conductor as abscissas, for substantially sta¬ 
tionary conditions. 

Coefficient of Coupling, Inductive —The ratio of 
the effective mutual inductance of two cir¬ 
cuits to the square root of the product of the 
effective self-inductances of each of these 
circuits. 

Coherer —A device sensitive to radio frequency 
energy, and characterized by (1) a normally 
high resistance to currents at low voltages. 

(2) A reduction in resistance on the applica¬ 
tion of an increasing electromotive force, and 

(3) the substantial absence of thermo-electric 
or rectifying action. 

Communication, Radio —The transmission of sig¬ 
nals by means of electro-magnetic waves orig¬ 
inating in a constructed circuit. 

Compass, Radio —A radio receiving device for de¬ 
termining the direction (or the direction and 
its opposite) of maximum radiation. 

Condenser, Air —A condenser having air as its 
dielectric. 

Condenser, Compressed Gas —A condenser hav¬ 
ing compressed gas as its dielectric. 

Corona —See Brush and Corona losses. 


172 RADIO 

Counterpoise —A system of electrical conductors 
forming one portion of a radiating oscillator, 
the other portion of which is the antenna. In 
land stations, a counterpoise forms a capaci¬ 
tive connection to ground. 

Coupler —An apparatus which is used to transfer 
radio frequency energy from one circuit to 
another by associating portions of these cir¬ 
cuits. 

Coupler, Capacitive —An apparatus which, by 
electric fields, joins portions of two radio¬ 
frequency circuits; and which is used to 
transfer electrical energy between these cir¬ 
cuits through the action of electric forces. 

Coupler, Direct —A coupler which magnetically 
joins two circuits having a common con¬ 
ductive portion. 

Coupler, Inductive —An apparatus which by mag¬ 
netic forces joins portions of two radio fre¬ 
quency circuits and is used to transfer elec¬ 
trical energy between these circuits through 
the action of these magnetic forces. 

Coupling —See coefficient of coupling (Inductive). 

Current, Damped Alternating —An alternating 
current whose amplitude progressively di¬ 
minishes (also called oscillating current). 


DEFINITIONS 


173 


Current, Forced Alternating —A current, the fre¬ 
quency and damping of which are equal to 
the frequency and damping of the exciting 
electromotive force. See further Current, 
Free Alternating. 

Note—During the initial stages of excita¬ 
tion, both free and forced current co-exist. 

Current, Free Alternating —The current follow¬ 
ing any transient electromagnetic disturb¬ 
ance in a circuit having capacity, inductance 
and less than the critical resistance. See fur¬ 
ther. Eesistance, Critical. 

Curve, Distribution, of a Radio Transmitting 
Station for a Given Distance —This is a polar 
curve the radii vectors of which are propor¬ 
tional to the field intensity of the radiation 
at that distance in corresponding directions. 
See also Compass, Eadio. 

Note 1—The distribution curve depends, 
in general, not only on the form of the an¬ 
tenna, but also on the nature of the ground 
surrounding the station. 

Note 2—The distribution curve generally 
varies with the distance from the station. 

Curve, Resonance, Standard —A curve the ordi¬ 
nates of which are the ratios of the square of 


174 


RADIO 


the current at any frequency to the square 
of the resonant current, and the abscissas are 
the ratio of the corresponding wave length 
to the resonant wave length; the abscissas 
and ordinates having the same scale. 

Cyclogram —See Characteristic, Dynamic. 

Cyclograph —An instrument for the production of 
cyclograms. 

Decrement —See Decrement, Linear, and Logar¬ 
ithmic. 

Decrement of a Linearly Damped Alternating 
Current —This is the difference of successive 
current amplitudes in the same direction, di¬ 
vided by the larger of these amplitudes. 

Decrement, Logarithmic, of an Exponentially 
Damped Alternating Current —This is the 
logarithm of the ratio of successive current 
amplitudes in the same direction. 

Decremeter —An instrument for measuring the 
logarithmic decrement of a circuit or a train 
of electromagnetic waves. 

Detector —That portion «of the receiving appar¬ 
atus which, connected to a circuit carrying 
currents of radio frequency, and in conjunc¬ 
tion with a self-contained or separate indica¬ 
tor, translates the radio frequency energy in- 


DEFINITIONS 


175 


to a form suitable for the operation of the 
indicator, such for instance, as a pair of tele¬ 
phone receivers. This translation may be 
effected either by the conversion of the radio 
frequency energy, or by means of the con¬ 
trol of local energy by the energy received. 

Device, Acoustic Resonance —A device which util¬ 
izes in its operation resonance to the radio 
frequency of the received signals. 

Diplex Reception —The simultaneous reception of 
two signals by a single operating station. 

Diplex Transmission —The simultaneous trans¬ 
mission of two signals by a single operat¬ 
ing station. 

Duplex Signaling —The simultaneous reception 
and transmission of signals. 

Excitation, Impulse —A method of producing free 
alternating currents in an excited circuit in 
which the duration of the exciting current is 
short compared with the duration of the ex¬ 
cited current. 

Note—The condition of short duration im¬ 
plies that there can be no appreciable re¬ 
action between the circuits. 

Factor, Damping —The product of the logarithmic 
decrement and the frequency of an ex- 



176 


RADIO 


potentially damped alternating current. 

Factor, Form —The form factor of a symmetrical 
antenna for a given wave length is the ratio 
of the algebraic average value of the E. M. S. 
currents measured at all heights to the great¬ 
est of these R. M. S. currents. 

Note 1—For a given R. M. S. current at the 
base of the antenna, the field intensity at dis¬ 
tant points is proportional to the form factor 
times the height of the antenna. 

Note—The effective height ( height of cen¬ 
ter of capacity) is equal to the form factor 
times the actual height of the antenna. 

Note 3—The form factor varies in a given 
antenna at various wave lengths due to var¬ 
iation of the current distribution. 

Frequencies, Audio (abbreviated a . /.)—The fre¬ 
quencies corresponding to the normally aud¬ 
ible vibrations. These are assumed to lie 
below 10,000 cycles per second. 

Frequencies, Radio (abbreviated r. /.)—The fre¬ 
quencies higher than those corresponding to 
the normally audible vibrations, which are 
generally taken as 10,000 cycles per second. 
See Frequencies, Audio. 

Note—It is not implied that radiation can- 


DEFINITIONS 


177 


not be secured at lower frequencies, and the 
distinction from audio frequencies is merely 
one of definition based on convenience. 

Frequency, Changer —See Changer Frequency. 

Frequency, Group —The number per second of 
periodic changes of amplitude or frequency 
of an alternating current. 

Note 1—Where there is more than one per¬ 
iodically recurrent change of amplitude, or 
frequency, there is more than one group fre¬ 
quency present. 

Note 2—The term “group frequency’’ is 
often called by the term “spark” frequency.” 

Frequency Transformer —See Changer, Fre¬ 
quency. 

Fundamental of an Antenna —This is the lowest 
frequency of free oscillations of the unloaded 
antenna (No series inductance or capacity). 

Fundamental Wave Length —The wave length 
corresponding to the lowest free period of 
anv oscillator. 

Gap Micrometer —A device for protecting any 
apparatus from excessive potentials, and con¬ 
sisting of a short gap designed for very fine 
adjustment. 

Ground —A conductive connection to the earth. 


178 


BADIO 


Impulse Excitation —See Excitation, Impulse. 

Interference, Wave (In Radio Communication )— 
The reinforcement or neutralization of 
waves, arriving at a receiving point along 
different paths from a given sending sta¬ 
tion; (to he distinguished from ordinary or 
station interference, which is simultaneous 
reception of signals from two or more sta¬ 
tions). 

Key —A switch arranged for rapidity of manual 
operation and normally used to form the 
code signals of a radiogram. 

Key y Relay —See Belay Key. 

Lengthy Wave —See Wave Length. 

Losses, Brush or Corona —See Brush and Corona 
Losses. 

Meter, Wave —See Wave Meter. 

Oscillations (In Radio Worlc) —See Current, 
Damped Alternating. 

Oscillatory Arc —See Arc Oscillator. 

Potentiometer —As commonly used for radio re¬ 
ceiving apparatus, a device for securing a 
variable potential by utilizing the voltage 
drop across the variable portion of a current 
carrying resistance. 


DEFINITIONS 


179 


Radiation, Sustained —See Waves, Sustained. 

Radiogram —A telegram sent by radio. 

Radio Telephone —An apparatus for the trans¬ 
mission of speech by radio. 

Rectifier, Electron —A device for rectifying an 
alternating current by utilizing the approxi¬ 
mately unilateral conductivity of a hot ca¬ 
thode and a relatively cold anode in so high a 
vacuum that a pure electron current flows 
between the electrodes. 

Rectifier, Gas —An electron rectifier containing 
gas which modifies the internal action by the 
retardation of the electrons or the ionization 
of the gas atoms. 

Relay, Electron —A device provided with means 
for modifying the pure electron current flow¬ 
ing between a hot cathode and a relatively 
cold anode placed in as nearly as possible a 
perfect vacuum. These means may be, for 
example, an electric control of the pure elec¬ 
tron current by variation of the potential of 
a grid interposed between the cathode and 
the anode. 

Relay, Gas —An electron relay containing gas 
which modifies the internal action by the re- 


180 


RADIO 


tardation of the electrons or the ionization of 
the gas atoms. 

Relay Key —An electrically operated key. See 
further, Key. 

Resistance, Antenna —See Antenna Eesistance. 

Resistance, Critical, of a Circuit —That resistance 
which determines the limiting condition at 
which the oscillatory discharge of a circuit 
passes into an aperiodic discharge. 

Resistance, Effective, of a Spark —The ratio of 
power dissipated by the spark to the mean 
square current. 

Resistance, Radiation —This is the ratio of the to¬ 
tal energy radiated (per second) by the an¬ 
tenna to the square of the R. M. S. current 
at a potential node (generally the ground 
connection). See further, Antenna Resist¬ 
ance. 

Resistance, Radio Frequency —This is the ratio 
of the heat produced per second in watts to 
the square of the R. M. S. current (r. f.) in 
amperes in a conductor. 

Resonance —Resonance of a circuit to a given ex¬ 
citing alternating electromotive force is that 
condition due to variation of the inductance 
or capacity in which the resulting effective 


DEFINITIONS 181 

current (or voltage) in that circuit is max¬ 
imum. 

Note 1—Instead of varying the inductance 
and capacity of a circuit the frequency of the 
exciting field may he varied. The condition 
of resonance is determined by the frequency 
at which the current (or voltage) is a max¬ 
imum. 

Note 2—The resonance frequency corre¬ 
sponds the more accurately to the frequency 
of the free oscillations of a circuit, the lower 
the damping of the exciting alternating field 
and of the excited circuit. 

Resonance , Acoustic Device —See Device Acous¬ 
tic Resonance. 

Resonance, Sharpness of —See Tuning, Sharp¬ 
ness of. 

Sharpness of Tuning —The measure of the rate 
of diminuation of current in transmitters and 
receivers with detuning of the circuit which 
is varied. 

Spark —An arc of short duration. 

Static —Disturbances caused by atmospheric 
charging of the antenna. 

Note—When it is definitely known that dis¬ 
turbances are due to atmospheric charging 



182 


RADIO 


of the antenna, the word “Static’’ is used. 
In general disturbances are called ‘ ‘ Strays. ’ 9 

Strays —Electromagnetic disturbances set up by 
distant discharges. See Static. 

Train, Wave —The waves emitted which corre¬ 
spond to a group of oscillations in the trans¬ 
mitter. See also, Frequency Group. 

Transformer —A device for transferring elec¬ 
trical energy from one state to another. In 
radio we have a variety of transformers for 
various purposes. There are power trans¬ 
formers, oscillation transformers, amplify¬ 
ing transformers, telephone transformers, 
etc. 

Tuning —The process of securing the maximum 
indication by adjusting the same time period 
of a driven element. See Eesonance. 

Tuning, Sharpness of —See Sharpness of Tuning. 

Vacuum Tube, Three Electrode —See Belays, 
Electron and Gas. This tube is also known 
as an “Audion.” 

Vacuum Tube, Two Electrode —See Rectifiers, 
Electron and Gas. This tube is also known 
as a ‘ i Fleming Valve.” 

Waves, Electromagnetic —A periodic electromag¬ 
netic disturbance through space. 


DEFINITIONS 


183 


Wave Length (of an Electromagnetic Wave )— 
The distance in meters between two consecu¬ 
tive maxima, of the same sign, of electric and 
magnetic forces. In other words, the dis¬ 
tance from crest to crest of two waves. 

Wave Length f Fundamental —See Fundamental 
Wave Length. 

Wave Length, Natural —In a loaded antenna (that 
is, with series inductance or capacity) the 
natural wave length corresponds to the low¬ 
est free oscillation. 

Wave Changer —See Changer, Wave. 

Wave Meter —A radio frequency measuring in¬ 
strument, calibrated to read wave lengths. 

Alternator —Is a device for converting mechan¬ 
ical energy into alternating current. 

Alternator, High Frequency —Is an alternating 
current generator for radio frequency having 
a rotor of solid steel shaped as a disc for 
maximum strength and provided with in¬ 
ductor poles, and having stationary arma¬ 
tures with radial faces on both sides of the 
rotating disc. 

Audion —The audion is a relay, operated by elec¬ 
trostatic control of currents flowing across 
a gaseous medium. In its present commer- 


184 


RADIO 


cial form, it consists of three electrodes in 
an evacuated bulb, one of these electrodes 
being a heated metal filament, the second a 
grid-like electrode, and the third a metal 
plate; an input circuit connected to the fila¬ 
ment and the grid; and an output circuit con¬ 
nected to the filament and the plate, includ¬ 
ing a local source of energy and a telephone 
receiver. 

Chopper —A transmitting device for repeatedly 
changing circuit connections at a uniform 
high rate of speed. The object of the above 
operation is to cause a continuous variation 
at audio frequency of the energy radiated at 
a fixed wave length from an antenna. 

Gap, Quenched —A spark gap provided for mini¬ 
mizing arcing and generally used under con¬ 
ditions which prevent the re-transfer of 
energy between the primary and secondary 
oscillation circuits. 

Gap, Synchronous, Rotary —A rotary spark gap 
which produces discharges in synchronism 
with the supply of alternating electromotive 
force. 

Gap, Rotary Non-Synchronous —A rotating gap 
for increasing low frequency spark dis¬ 
charges to a higher spark frequency. 


DEFINITIONS 


185 


Eeterdyne —A receiver for radio frequencies 
which operates by the production of inter¬ 
ference beats between two radio frequency 
currents or voltages, the source of one of 
these radio frequencies being located at the 
receiving station. 

Kenotron —Kenotron is a name applied to a gen¬ 
eral class of apparatus having an incandescent 
cathode and operating with a pure electron 
discharge in a vacuum so high that gas ioni¬ 
zation plays no essential role. One of the uses 
of the kenotron is the rectification of alternat¬ 
ing current, particularly of high voltages. 

Pliotron —A pliotron is a kenetron provided with 
a member for electrostatically controlling the 
electron discharge. 

Tikker —A receiving device for changing circuit 
connections in such a manner as to render 
the sustained radio frequency electrical 
energy stored in an oscillating circuit, avail¬ 
able for operating a telephone receiver. 

Wave y Damped —Damped oscillations are those 
consisting of a series of alternating currents 
of gradually decreasing amplitude. 

Wave , Undamped —Is a continuous wave which 
has a constant amplitude. 


186 RADIO 

Wave, Continuous —See Wave, Undamped. 

Wave, Sustained —See Wave, Undamped. 

Capacity —A term chiefly employed in connection 
with condensers. A condenser stores elec¬ 
tricity, the amount stored depending upon 
the capacity of the condenser. Capacity is 
measured in “farads.” Capacities used in 
radio are so small that the farad is too large 
for practical use, therefore the unit employed 
is the microfarad (abbreviated m. f. d.) or 
one millionth of a farad. 

Condenser —Refer to capacity. The condenser 
stores electricity. It consists generally of 
alternate layers of conductor and non-con¬ 
ductor, the latter being termed the dielectric. 

Alternation —An alternation of current is one- 
half cycle or the rise and fall of an alternat¬ 
ing current in one direction. There are two 
alternations to a cycle. 

Cycle —A complete reversal of current. A cycle 
consists of two alternations. Further, see 
Alternation. 

Alternating Current (abbreviated A. C.) —An al¬ 
ternating current is electromotive force that 
gradually flows from a zero to a maximum 
value in one direction, then decreases again 


DEFINITIONS 


187 

to zero, rises in maximum value in the oppo¬ 
site direction and again decreases to zero. 
This is repeated over and over again. The 
number of repetitions per second determining 
the frequency of the alternating current. 

Aerial —See Antenna. 

Inductance —Is that property of a circuit by which 
electrical energy may be stored in electro¬ 
magnetic form. 

Self-Induction —Phenomena arising from the rise 
and fall of a magnetic field about a coil of 
wire, through which an electrical current is 
passing. It is the property of an electrical 
circuit which tends to prevent a change of 
the electric current established in it. 

Mutual Induction —Is induction due to two inde¬ 
pendent circuits reacting on each other. In 
other words, the electromotive force induced 
in one of the circuits when the current in the 
other is changing at its unit rate per second. 

Period —A period is the time required for a cycle 
of alternating current to pass through all its 
values. The period of a cycle determines the 
frequency of the current per second. 

Frequency —Is the number of cycles taking place 
in an alternating current in a second of time. 


188 RADIO 

Frequency, High —An alternating current where 
frequencies counted in thousands take place 
in a second of time. 

Frequency, Low —An alternating current where 
frequencies counted in tens or hundreds take 
place in a second of time. These are gen¬ 
erally from 60 to 500 cycles per second. 

Oscillatory Currents (Audio Frequency) —Vibra¬ 
tions within the range of audibility of the 
human ear. Generally considered those of a 
frequency less than 10,000 per second. 

Oscillatory Currents (Radio Frequency) —Vibra¬ 
tions above the range of audibility of the 
human ear, generally considered frequencies 
beyond 10,000 per second. 

Frequency Spark —The number of spark dis¬ 
charges per second across a spark gap. 

Frequency , Tone —See Frequency, Spark and 
Frequency, Group. 

Oscillatory Circuit —A circuit permitting a free 
flow of oscillations, generally consisting of a 
wire coil in series with a condenser. 

Syntonic Circuits —Are several circuits having 
the same natural period of oscillation. 

Flux —A term designating the lines of magnetic 
or static force in any given space. 


DEFINITIONS 


189 


Flux Density —The number of electrostatic or 
electromagnetic lines per force per square 
centimeter. 

Electromagnetic Lines of Force —Lines of strain 
about the poles of a permanent or electro¬ 
magnet, or in a wire in which an electric cur¬ 
rent is flowing. 

Electrostatic Lines of Force —Lines of strain 
about a body containing an electrostatic 
charge. 

Reactance —A term used to express the resistance 
of a conductor to any changes of current in it. 

Impedance —A term to express the opposition of 
a circuit to a varying current, due to the re¬ 
sistance and reactance of a circuit. 

Volt —The unit of electromotive force. 

Ampere —The unit of current. 

Ohm —The unit of resistance. 

Watt —The unit of power. 

Coulomb —The unit of quantity. 

Farad —The unit of capacity. 

Henry —The unit of inductance. 

Ampere-Hour —The unit expressing the quantity 
of current passing through a circuit when one 
ampere flows therein for one hour of time. 




190 RADIO 

Rheostat —A device for regulating the resistance 
used for governing the flow of current in elec¬ 
trical circuits. They may be of a fixed or a 
variable standard. 

Reactance Coil —A coil with a variable “choking” 
effect used for a double purpose. It regu¬ 
lates the current flowing in the primary or 
secondary windings of a transformer, also 
to place the circuit consisting of the alternat¬ 
or and primary winding of the transformer 
in resonance with the circuit containing the 
secondary windings of the transformer and 
the condensers. 

Oscillation Transformer —A device to transfer 
oscillations of radio frequency from the 
closed oscillatory circuit, to the open or 
antenna circuit of a radio transmitter. 

Antenna Tuning Inductance —A wire coil used to 
increase the inductance in the antenna circuit 
and regulating the radiated energy. 

Change Over Switch —A device for the conven¬ 
ient and rapid shifting of the antenna from 
the receiving to the transmitting apparatus. 
This is also called an antenna or transfer 
switch. 

Tuner —A receiving device for transforming 


DEFINITIONS 


191 


energy absorbed by a receiving antenna and 
transferred to a detector circuit. It also per¬ 
mits an operator to conveniently tune in elec¬ 
tromagnetic waves of varying wave lengths. 

Condenser, Stopping —Used in receiving appar¬ 
atus to prevent the flow of battery current 
through the tuning coil of the closed oscil¬ 
latory circuit instead of through the crystal 
detector, as intended. It is also used in shunt 
to the receiving head phones to assist in the 
intensification of signals. 

Direct Current —An electrical current flowing 
constantly in one direction. 

Kilowatt —One thousand watts of power. 

Selectivity —The term used to express the ability 
to select any wave length to the exclusion of 
other wave lengths. 


CHAPTER XI 


QUESTIONS AND ANSWERS 

The following are questions the writer antici¬ 
pates may occur to the mind of the reader. Many 
are taken from the questions put to a commercial 
operator w T hen he is examined by the Federal 
Radio Inspector for his license. Others are 
dictated by the trend of questions asked by 
experimenters in the question columns of radio 
publications. These in conjunction with the defi¬ 
nitions contained in the preceding chapter, may 
be useful in explanation of some point not clari¬ 
fied in the other pages of this volume. 

Q. 1. Describe the construction of some form 
of standard wavemeter 

A . The following briefly described a simple 
wavemeter manufactured and used by the Marconi 
Company of America. It consists of a variable 
condenser to which is connected an inductance 
coil of a fixed given value. The inductance is 
attached to the condenser by means of a flexible 
cord so it can be placed in any position desired, 

192 







QUESTIONS AND ANSWERS 193 

while the variable condenser is placed at some 
distance from the circuit to be measured. A car- 
borandum crystal is connected in series with the 
head telephones, both are then connected in shunt 
to the variable condenser. A small glow lamp is 
included in series with the coil, and may he cut 
out of the circuit by means of the switch indi¬ 
cated. 

A scale is placed directly on the variable con¬ 
denser, which in turn moves under a stationary 
pointer. The scale reading of the condenser may 
be graduated directly in wave lengths or the data 
may be plotted in the form of a curve in the terms 
of an empirical scale on the condenser. These 
calibrations are obtained by comparing the wave- 
meter to a standard oscillatory circuit or by 
calculation of the constants in the wavemeter 
itself. 

The point of resonance on the wavemeter may 
be located either by a lamp in series with the cir¬ 
cuit, by a crystal detector and head telephones in 
shunt to the condenser, a hot wire milli-ammeter 
in series with the wavemeter, a Neon gas tube in 
shunt to the variable condenser, or a crystal 
detector and head ’phones connected unilaterally 
to a binding post of the variable condenser. 

Certain types of wavemeters have a variable 


194 


EADIO 


inductance and a fixed capacity, while others may 
have a variable inductance and a variable 
capacity. 

In using a wavemeter care must be taken that 
the coil of the wavemeter bears a certain relation 
to the circuit under measurement, otherwise it 
will not he cut by the lines of force. 

Q. 2. If your hot-wire ammeter broke, or such 
an instrument was not available, what simple 
device can be substituted to show when a point of 
resonance is reached, or to show a maximum of 
radiation? 

A. Several arrangements may be made. The 
best is a method using a small four-volt incan¬ 
descent electric lamp, connected in series in the 
lead to ground of the open or antenna circuit. 
With this arrangement the lamp, for protection, is 
shunted by a loop of wire, preferably having a 
sliding contact. When the correct point of reso¬ 
nance is obtained with the open and closed 
oscillatory circuits, the lamp will light with a 
maximum glow. 

Another method is to place a very short gap in 
the same lead described above. When resonance 
is reached, there will be a maximum amount of 
discharge across the gap. This method is not con- 


QUESTIONS AND ANSWERS 195 

sidered a good one to maintain permanently in 
the circuit, as it increases the resistance of the 
antenna circuit. 

Q. 3. What are the advantages of a high fre¬ 
quency spark dischargerf 

A . There are several excellent advantages. 

1. The signals emitted from such a spark are 
more readily detected above atmospheric disturb¬ 
ances or static. 

2. The telephone receivers used in modern 
radio practice is more sensitive to such a fre¬ 
quency than to the lower frequencies. 

3. A better manipulation of the characters of 
the Morse Code can be obtained by means of the 
telegraph key when high frequency is used than 
when low frequencies are employed. Thus a 
faster rate of signalling can be obtained. 

An additional advantage is that higher fre¬ 
quencies permit the use of a smaller condenser, 
with a resultant decrease in the strain upon 
insulators. 

Q. 4. What are the advantages of a quenched 

gapf 

A. The quenched gap possesses numerous 
advantages, principally as follows: 


196 


EADIO 


1. The oscillations in the closed oscillatory cir¬ 
cuit are quickly damped out, thus permitting the 
antenna circuit to vibrate in its own natural 
period without any reaction upon the closed 
circuit. 

2. It is comparatively noiseless in use. 

3. Permits of the use of low voltage trans¬ 
formers. An economy in both space and expense. 

Q. 5. Why is alternating current desirous as a 
source of electromotive force in radio-telegraphy? 

A. By using alternating current the neces¬ 
sity of using devices for making and breaking 
direct current is obviated. Mechanical or electro¬ 
lytic vibrators are limited to the practical use of 
power less than one kilowatt, whereas the use of 
power utilizing alternating current is practically 
unlimited. 

Q. 6. If your spark suddenly stopped while 
sending, give the order in which you ivould look 
for the trouble and the method of repair for each 
possibility . 

A. The search should be in the following 
order: 

1. Make or find a circuit diagram, unless thor- 

\ 

oughly familiar with the connections and 
positive they are right. 


QUESTIONS AND ANSWERS 197 

In drawing diagram follow each branch 
of the circuit from the source (+ terminal 
of battery or generator armature) com¬ 
pletely around (through the ~ terminal) to 
the place of beginning. Remember that no 
current will flow in a circuit or any part of 
a circuit unless there is a difference of 
potential in it. 

2. Trace the wiring according to the diagram. 

3. While tracing, see that— 

(A) Fuses are good, if any are in the cir¬ 

cuit. 

(B) Connections are clean and good. 

(C) Contact is not prevented by insulating 

caps of binding screws or insulation 
of wire. 

(D) Wires do not touch, making short cir¬ 

cuits. 

(E) There are no extra wires or connec¬ 

tions. 

(F) There are no breaks in the wire inside 

of insulation. This occasionally 
happens with old lamp cord. The 
broken place is very limber, and can 
be pulled in two more readily than a 
sound place. 

4. Look for defects in the apparatus itself. 


198 


RADIO 


In a generator, besides loose connections, 
electrical troubles easily remedied are, for 
direct current. 

5. Failures to generate electromotive force, 
caused by— 

(A) Brushes not in the right place. On 

nearly all direct current machines of 
reasonably modern construction, the 
proper position for brushes on the 
commutator is nearly opposite the 
middle of the field poles, or slightly 
forward (in the direction of rota¬ 
tion) of that point. The exact loca¬ 
tion, found by trial, is that 
which gives sparkless commutation. 
Brushes are set right at the factory, 
and should be left as they are, unless 
there is a good reason to believe that 
thev have since been shifted. 

(B) Brushes not making good contact be¬ 

cause of bad fit or too little pressure. 
Test by lifting them slightly, one by 
one, to detect loose springs, also try 
pressing brushes to commutator 
with a dry stick. Remedy by work¬ 
ing fine sandpaper back and forth, 
sharp side out, between the commu- 


QUESTIONS AND ANSWERS 199 

tator and brush (holding it in such a 
way that the toe of the brush is not 
ground off) or by tightening the 
brush springs, as needed. 

Brushes are designed, either to 
press against the commutator 
squarely, pointing toward the center 
of the shaft, or, more commonly to 
trail somewhat as an ordinary paint 
brush might trail if held against the 
commutator. However, there is also 
in very satisfactory use a form of 
holder by which the brushes are held 
pointing against the direction of 
rotation. Instead of sliding up or 
down in a box they are pressed 
against a smooth face of brass by 
springs. 

(C) Field connections reversed. 

6. Sparking, when caused by— 

(A) Roughened commutator, cured by 

holding fine paper (not emory) 
against it while running. 

(B) Brushes shifted, for remedy see 5 

above. It is very important that all 
the brushes be at the proper points. 
This means, for example, that if the 


P ' JIO 


200 

* 

brushes are supposed to touch at 
four poin' , spaced a quarter way 
round the commutator, they shall 
actually be a quarter of a circumfer¬ 
ence apart, as tested by fine marks 
on a strip of paper held against the 
commutator. 

7. Heatings of commutator due to brush fric¬ 

tion. Reduce tension of springs. 

In alternating current generators look 
for— 

8. Loose connections and bad contacts at 

brushes. Position of brushes on collector 
rings is immaterial, as there is no commu¬ 
tation on an a.c. machine. 

In d.c. shunt motors, motor generators, 
or dvnamotors, the simple troubles are: 

9. Failure to start, or starting too suddenly 

with speed quickly becoming excessive, due 
to wrong connections. 

10. Sparking, caused by excessive lead or wrong 
brush position. See 5 or 6 above. 

The proper position for motor brushes is 
slightly backward (against the direction of rota¬ 
tion) of the center of the field poles. 

Having thus traced the motor-generator cir¬ 
cuits, the fault may lie in transformer or the radio 


QUESTIONS AND ANSWERS 201 

circuits. These should be traced successively as 
follows: 

The primary winding of the power transformer 
may be burnt out. If the voltage is 110 volts, this 
can be tested with an ordinary test lamp. As a 
rule the primary, consisting of a few turns of 
heavy wire, can be easily repaired. If the test 
indicates it is in the secondary winding of this 
transformer, the trouble may be more difficult to 
remedy. Most radio power transformers have a 
secondary built in sections, in this case it may be 
possible to remove the burnt out section. Unless 
another is available and substituted, it would be 
necessary to reduce the primary voltage, if the 
transformer is operated short of one or more 
sections. 

If the fault is a punctured condenser, and no 
spares available, the punctured unit can be re¬ 
moved and the remaining units placed in a 
parallel connection, affording the same capacity 
as formerly employed, but again the primary 
potential must be reduced, as supplied to the 
transformer. 

If a plain gap is used, it may be found that the 
electrodes have either fallen together, shorting 
the circuit, or becoming too far apart, the spark 
will not discharge across the gap. 


202 


RADIO 


If a quenched gap is in use, there may be a short 
circuit caused by the contact of the sparking sur¬ 
faces with each other, or by the destruction of the 
insulation between the sparking surfaces. 

Q. 7. What is the effect of opening a spark gap 
too wide? 

A . It imposes an additional strain on the con¬ 
densers which may result in a puncture. The 
spark also becomes rough or “stringy,’’ with a 
resultant poor tone. It also imposes an extra 
strain on the windings of the secondary of the 
transformer. 

Q . 8. What is the effect of connecting two equal 
banks of transmitting condensers in series9 

A. The total capacity of the condenser is re¬ 
duced to one-half of one bank, but the strain of 
the potential on the dielectric is divided equally 
between the two units, thereby protecting the 
condensers from possible puncture. 

Q. 9. What is the effect on the adjustment of a 
transmitter if the coupling is considerably in¬ 
creased? 

A. Oscillations of two different frequencies will 
be radiated from the antenna. If the coupling is 


QUESTIONS AND ANSWERS 203 

too close, the energy will be distributed over sev¬ 
eral of wave lengths, causing considerable inter¬ 
ference over a wider range of wave lengths. 

Q. 10. How are the very high voltages pro¬ 
duced for radio telegraphic purposes? 

A. By means of step-up alternating current 
transformers. 

Q. 11. Name some of the commercial fre¬ 
quencies which are employed in radio telegraphic 
work? 

A. 60, 120, 240, 480 and 500 cycles per second. 

Q. 12. What is the most common cause for the 
breakdown of high potential condensers? 

A. A spark gap which is too wide. Also if the 
dielectric is of glass, a flaw in the glass may cause 
a puncture. 

Q. 13. What is meant by a pure wave in radio 
telegraphy? 

A. If there are two waves emitted by a trans¬ 
mitter, a wave is considered “pure” when the 
amplitude of the lesser wave is less than two- 
tenths of that in the greater wave. 

Q. 14. Describe a method for protecting high 
potential condensers from puncture. 


204 


RADIO 


A. By placing a spark discharge safety gap 
across the terminals. This may he adjusted so 
that an excessive potential would discharge across 
the safety gap, if for some reason the spark gap 
of the transmitter failed to function. Also the 
condenser units may consist of two or three banks 
in series or in series parallel, this dividing the 
voltage between them. 

Q. 15. What is the effect of placing a condenser 
in series with an antenna? 

A. The total capacity of the antenna is re¬ 
duced, sometimes by nearly 50 per cent, thus 
reducing the wave length. 

Q. 16. What is the advantage in having more 
than one wire in the antenna for transmitting pur¬ 
poses? 

A. A slight advantage in increased radiation, 
hence increased transmitting range. This is 
caused by the additional wires increasing the 
capacity, decreasing the effective inductance and 
decreasing the frequency resistance. 

Q. 17. Hoiv can you tell if your antenna is 
radiating? Describe the apparatus used. 

A. By attempting communication with a dis¬ 
tant station. Although instruments may indicate 


QUESTIONS AND ANSWERS 205 

a strong current flow in the antenna, sometimes 
there is poor radiation. When the set is first 
placed in resonance, a note should be made of the 
original results obtained. Should these values 
later fall off, it would be a good indication that 
something is wrong and that the radiation is not 
normal. 

Q. 18. What are the uses of a lightning switch , 
and also, a protective air gap? 

A. Such a switch is used to disconnect, when 
not in use or during a heavy storm, all transmit¬ 
ting and receiving apparatus from the antenna. 
The latter is then grounded by means of the 
switch. The use of such a switch is made arbi¬ 
trary in some cities by the Boards of Fire Under¬ 
writers. 

An air gap is a small gap which permits any 
heavy excessive current, such as lightning, to 
jump the gap, one side of which is grounded. The 
use of this gap has recently been made mandatory 
in New York City by the Board of Fire Under¬ 
writers. 

Q. 19. Does a wave of high decrement refer to 
a “broad” or a “sharp” wave? 

A. If the emitted wave of a station possesses a 


206 


EADIO 


high decrement, it will be broad as received and 
difficult to eliminate interference, but if of low 
decrement, sharp tuning at the receiving station 
will result. 

Q. 20. Why should all the joints in antenna 
wires be soldered? 

A. To eliminate resistance, for one thing, and 
to prevent losses of energy by corrosion. It is 
particularly important in receiving aerials. Care 
must be taken, however, that not too much heat is 
applied when soldering, or the wire will be weak¬ 
ened. There is a device called a MacIntyre sleeve 
that answers even better than soldering in making 
joints. 

Q. 21. What is the effect on radiation and 
range if the insulation of the antenna is poor? 

A. It will reduce the range very considerably. 
Leaky insulators cause so much energy to be lost 
and therefore the range of the station is very 
greatly reduced. 

Q. 22. What effect has the height of the an¬ 
tenna upon the range of the station? 

A. Generally speaking, authorities appear to 
agree that the higher the aerial, the greater will 
be the displacement current established about the 


QUESTIONS AND ANSWERS 207 

antenne. Experiments, especially recently,'have 
upset many of the theories regarding this subject. 
Experience broadly shows that a high antenna 
and a good ground provide a station with a 
greater range. 

Q. 23 What is the effect of tightening the 
coupling of the receiving tuner? 

A. It has the effect of increasing the damping 
of the receiving set, thus allowing a response to 
several wave lengths. When the coupling is in¬ 
creased, it increases the mutual inductance 
between the primary and secondary windings, 
thus more energy is transferred than when a 
lesser coupling is employed. 

Q. 24. If your head telephone circuit is found 
open, where is the trouble most likely to be and 
how would you remedy it? 

A. Probably the fault may be found in the 
cords, a disconnection at the metal tips, or at the 
binding posts on the ear pieces of the phones. If 
the cord is worn out, ordinary wire may be sub¬ 
stituted, preferably flexible lamp cord, untwisted. 
If the fault is in the magnets, the job will be more 
difficult and will necessitate sending it to the 
manufacturer for repair, or some other expert. 


208 


RADIO 


Q. 25. If the natural period or the fundamental 
wave length of an antenna is too long to receive 
short wave lengths, how would you proceed to 
adopt it for short wave lengths without shorten¬ 
ing the antenna? 

A. Insert a variable condenser in series with 
antenna. The effective capacity of the antenna 
will thereby be reduced and consequently the wave 
length also. 

Q. 26. What precaution do you take to protect 
your receiving detector from being injured by 
nearby strong signals? 

A. The coupling between the primary and sec¬ 
ondary may be opened or the two circuits thrown 
out of resonance. 

Q. 27. What tests may be made to ascertain 
whether a vacuum tube is oscillating? 

A. A clicking sound will be heard in the tele¬ 
phones when the system is oscillating under the 
following conditions: 

1. When the tickler is short circuited. 

2. When the grid binding post is touched. 

3. When secondary inductance switch on, re¬ 
ceiver is moved from one contact to 
another. 


QUESTIONS AND ANSWERS 209 

If the buzzer is started when audion is oscillat¬ 
ing, a soft hissing noise will be heard in the 
telephones instead of the true note of the buzzer. 

Periodic clicks will be heard in the telephones if 
the tickler coupling is too tight and the grid leak 
not great enough. 

Q. 28. To what cause may failure to obtain 
oscillations in a vacuum tube be due f 

A . Failure to obtain oscillations may be due to 
the following causes: 

1. Reversed filament battery. 

2. Reversed plate battery. 

3. Reversed tickler leads. 

4. Reversed leads from the “audion” binding 

posts on the receiver to the RA and RE 
terminals on the vacuum tube control 
apparatus. 

5. Value of bridging condenser too small. 

6. Improper value of stopping condenser. 

7. Tickler too loosely coupled to the secondary. 

8. Value of plate current not sufficient. 

9. Bad cells in plate battery. 

10. Defective vacuum tube. 


CHAPTER XII 


HOW TO BUILD A SIMPLE RECEIVER 

The limited scope of this work precludes the 
possibility of entering into matters of design of 
all radio apparatus. However, it is thought that 
the beginner will obtain useful results from the 
set below described. This can be put together for 
less than thirty dollars. If the new experimenter 
later feels inclined to go in for a more elaborate 
equipment, the parts contained therein can be 
utilized to good advantage. 

This set was designed by the Bureau of Stan¬ 
dards to meet the public demand. With a suitable 
antenna and a reliable crystal for a detector, it 
should enable the user to read radio telegraph 
signals or music and voice over a range approxi¬ 
mating 50 miles, probably more, especially at 
night. 

The experience gained by a beginner in the con¬ 
struction and use of this simple receiver will be 
invaluable when he, or she, wishes to go further in 

the study of the art. The following described set 

210 




HOW TO BUILD A RECEIVER 211 

will receive signals between wave lengths of 200 
and 600 meters. 

Parts of Set .—The two-circuit or inductively 
coupled receiving set consists essentially of a 
coupler, a variable condenser, crystal detector 
and accessories. 

The assembled receiving set is shown in Fig. 
47; and Fig. 48 shows how to wire the set. 

The coupler, shown in left half of Fig. 47, is 
composed of a fixed section made up of the coil 
tube P, the upright J, the contact panel K, and 
the base B, and a movable section composed of 
coil tube S, the supporting contact panel M, and 
the base L. 

The following parts will be required: 

Jjist of Parts Required: 

6 ounces No. 24 double cotton covered copper 
wire; 

2 round cardboard boxes; 

3 switch knobs and blades, complete; 

24 switch contacts and nuts; 

3 binding posts, set screw type; 

4 binding posts, any type; 

1 crystal, tested; 

3 wood screws for fastening panel to base; 
wood for panels; 


212 


RADIO 


2 pounds paraffin; 
lamp cords; 
telephone receivers; 

1 battery clip for crystal; 
miscellaneous screws; 

1 variable condenser (capacity 0.0004 to 0.005 
microfarads). 

Instructions for Construction 

Instructions for making the movable coil of the 
coupler are as follows: 

The coil tube S, Fig. 47, is a piece of cardboard 



Fig. 47. Assembled two circuit receiving set with crystal 

detector. 

tubing 3% inches in diameter and 4 inches long. 
A round cardboard table salt box which can be 
obtained at a grocery store is about 3% inches in 












HOW TO BUILD A RECEIVER 213 



Fig. 48. Wiring diagram and details of two circuit re- 
ceiving set with crystal detector 


diameter and can be used for this purpose. One 
of the cardboard ends or caps should be securely 
glued to the box. 

This tube is wound with No. 24 (or No. 26) 
double cotton covered wire. 

To wind this wire punch two holes in the tube 
% inch from the open end, as shown at R, Fig. 48. 
Weave the end of the wire through these holes so 
that it is firmly anchored and has one end extend¬ 
ing about 10 inches inside the tube. Punch a hole, 
F, Fig. 48, about % inch from the other end 
(which has the cardboard cover secured to it) in 
line with the holes punched at R. Draw the free 
end of the wire through the inside of the tube, and 
thread it out through the hole at F. Now wind on 











































214 


RADIO 


ten turns of wire and take off a 6-inch twisted tap 
made by twisting a 6-inch loop of wire together at 
such a place that it will be slightly staggered from 
the first connection. Hold the turns tight and 
punch a hole, B, directly underneath the tap. 
Insert the end of the tap in the hole and pull it 
through the inside of the tube so that the turns 
are held in place. The hole for this tap should 
be slightly staggered from the first two holes 
which were punched. Punch another hole, L, % 
of an inch from the other end of the tube and in 
line with the hole B. Thread the twisted tap out 
through this hole and pull it tight. Wind on 10 
more turns and bring out another twisted tap; 15 
turns and another tap; 15 more turns and another 
tap. Finally wind on 20 more turns and bring out 
the free end of the wire in the same manner as the 
taps were brought out. The tube now has 80 
turns of wire wound on it and there are five 
twisted taps and two single wires projecting 
through the row of holes at the closed end of the 
tube. The position of the wires inside the coil 
tube is shown by the dotted lines. 

JBase and Support for Coil .—The con¬ 
tact panel M, Fig. 47, which supports the coil tube, 
is a piece of dry wood 5 y 2 inches long, 4 inches 
wide and y 2 inch thick. The end of the switch arm 


HOW TO BUILD A RECEIVER 215 


should be wide enough so that it will not drop 
between the contact points, but not so wide that it 
cannot be set to touch only a single contact. 
Having located the hole for the switch arm bolt, 
the switch arm should be placed in position and 
the knob rotated in such a manner that the end 
of the contact arm will describe an arc upon which 
the contact points are to be placed. The holes for 
the contacts should next be drilled, the spacing 
depending upon the kind of contacts that are to 
be used. 

The movable base L is a square piece of dry 
wood 4 inches long, 4 inches wide, % inch thick. 
Care should be taken to have the edges of this 
block cut square with respect to the sides. Now 
screw panel M to the movable base L, as shown in 
Fig. 47. Care should be taken to have the edges 
of the blocks M and L evenly lined up so that the 
two edges of the block L, Fig. 47, which slide along 
the inside edges of the stripe H and I, will be 
smooth, continuous surfaces. 

Fivced or Primary Coil .—The cardboard 
tubing for coil tube P is 4% inches in diameter by 
4 inches long. About two ounces of No. 24 (or No. 
26) double cotton covered copper wire is used 
for winding the coil. Punch two holes in the tube 
about one-half inch from the end. Weave the 


216 


RADIO 


wire through these holes in such a way that the 
end of the wire will be firmly anchored, leaving 
about 12 inches of the wire free for connecting. 
Start with the remainder of the wire to wind 
turns in a single layer about the tube, tightly and 
closely together. After one complete turn has 
been wound on the tube hold it tight and take off a 
tap. This tap is made as above described, by 
twisting a six-inch loop of wire together, tap at 
such a place that it will be slightly staggered from 
the first connection. Proceed in this manner until 
ten twisted taps have been taken off, one at every 
turn. After these first ten turns have been wound 
on the tube, and tapped, take off a six-inch twisted 
tap for every succeeding ten turns until seventy 
taps are taken off or seventy additional turns 
wound on the tube. After winding the last turn 
of wire anchor the end by weaving it through two 
holes punched in the tube as at the start, leaving 
about twelve inches of wire free for connecting. 
It is to be understood that each of the eighteen 
taps is slightly staggered to the right from the 
one just above, so that the taps will not be 
bunched along one line on the cardboard tube. 
See Fig. 48. It might be advisable after winding 
the tuning coil to dip the tuner in hot paraffin. In 
both primary and secondary, where each tap is 


HOW TO BUILD A DECEIVER 217 

taken off a very slight solder connection should 
be made to make perfect contact with the tap and 
wire of the coil. Glue a cardboard cover to the 
end of the tube where the single turn taps are 
taken off. 

The Panel .—Panel K should be made from a 
board 7% inches long by 4% inches wide and 
about y 2 inch thick. The position of the contacts 
can best be determined by inserting the switch 
arms in their respective holes and turning the 
knobs so that the ends of the switch arms will 
describe arcs. The position of the several holes 
for the binding posts, switch arms and switch con¬ 
tacts may first be laid out and drilled. 

The “antenna” and “ground’’ binding posts 
may be ordinary 8-32 brass bolts about iy 2 inches 
long with three nuts and two washers. The first 
nut binds the bolt to the panel, the second nut 
holds one of the short pieces of stiff wire, while 
the third nut holds the antenna or ground wire 
as the case may be. The switch arm with knob 
may be purchased in the assembled form or may 
be constructed from %-inch slice cut from a 
broom handle and a bolt of sufficient length 
equipped with four nuts and two washers, to¬ 
gether with a strip of thin brass. The end of the 
switch arm should be wide enough so that it will 


218 


RADIO 


not drop between the contact points, but not so 
wide that it cannot be set to touch only a single 
contact. The switch contacts may be of the regu¬ 
lar type furnished for this purpose, or they may 
be 6.32 brass bolts with one nut and one washer 
each. 

The fixed base B is a piece of dry wood 5 y 2 
inches wide, 11 inches long and between % and % 
inch thick. The support J, for fixed coil tube, is 
5y 2 inches wide (the width of the base), 6 inches 
long and about y 2 inch thick. This board should 
be screwed to one end of the base, so that it is held 
securely in a vertical position. It will then pro¬ 
ject about five inches above the base G. 

A strip of wood, 1,11 inches long, 5-16 inch wide 
and about % inch thick, is now fastened to the 
base by cigar-box nails or small brads, so that it 
is even with the rear edge, as shown in Fig. 47. 
The upright panel M, having been fastened to the 
movable base L, as previously explained, is placed 
in position as shown. The next step is to locate 
the strip H in such a position that the block L will 
slide easily back and forth the entire length of 
the fixed base B. Having found this position, this 
strip is secured in the same manner as the strip I. 
It is, of course, understood that neither the 
movable coil tube S, nor the switch contacts and 


HOW TO BUILD A RECEIVER 219 


binding posts have, np to the present time, been 
mounted on the upright panel M. The wooden 
parts for the loose coupler are now finished and 
should be covered with paraffin. 

It might be advisable after winding the coil 
tubes P and S to dip them in hot paraffin, this will 
help to exclude moisture. Have the paraffin 
heated until it just begins to smoke, so that when 
the coils are removed they will have a very thin 
coating of paraffin. 

Variable Condenser .—The variable air 
condenser, C, should have a maximum capacity of 
between 0.0004 and 0.0005 microfarads (400 to 500 
micromicrofarads). 

The type pictured in Fig. 47 is enclosed in a 
round metal case, but the unmounted type may 
also be used. The variable condenser is mounted 
on a board, R, Fig. 47, about 10 inches long, 5% 
inches wide and % inch thick. The strips of wood 
are fastened under the ends so that wires may 
be run underneath for the connections. After the 
holes for the detector binding post and also the 
holes for the telephone binding posts U, have 
been drilled, the board should be coated with 
paraffin. 

Crystal detector .—The galena crystal D 
may be mounted as pictured in Fig. 47 and Fig. 


220 


EADIO 


48. The holder for the crystal is a metallic pinch 
clip such as the ordinary battery test clip or small 
paper clip. This clip should be bent into a conven¬ 
ient shape so that it may be fastened to the base. 

The wire X which makes contact with the crys¬ 
tal is a piece of tine wire (about No. 30) which is 
wound into the form of a spring and attached 
(preferably soldered contact) to a heavy piece of 
copper wire (about No. 14). This heavy wire is 
bent twice at right angles, passes through the 
binding post and has a wood knob or cork fixed to 
its end as shown. It is desirable to have the fine 
wire of springy material, such as German silver, 
but copper wire may be used if necessary. 

The importance of securing a tested galena 
crystal cannot be emphasized too strongly, and it 
should be understood that good results cannot be 
obtained by using an insensitive crystal. 

Assembling Coupler .—The movable por¬ 
tion of the coupler should be assembled first. As 
shown in Fig. 47 the fittings making up this part 
of the set are the movable base L, the coil tube 
support M, the six switch contacts, the switch arm, 
and the binding posts, in the proper holes, which 
have been drilled. Adjust the switch arm until it 
presses firmly on the contact points (both heads) 
and fasten the bare end of a No. 24 copper wire 


HOW TO BUILD A RECEIVER 221 

between the nuts on the end of the switch arm 
bolt 2, Fig. 47 and Fig. 48, which projects through 
the panel M. Wind this wire into a spiral of two 
or three turns like a clock spring, leaving a few 
inches of the wire for connection. Insert two 
small screws V, Fig. 47, in the panel M, so that 
the switch arms will not drop off the row of con¬ 
tact points when the knob is turned too far. 

The coil tube S is now ready to be fastened in 
position on the panel M. Cut a one-inch hole in 
the cardboard end of the coil tube and place it 
with the closed end next to the panel M, in such a 
position that it will be just below the row of nuts 
and washers of the switch contacts, and in the 
center of the panel M, with respect to the sides. 
Fasten it to the panel with short wood screws. 
The switch arm bolt with the spiral wire con¬ 
nected to it should project through the hole cut 
in the end of the coil tube. Thread the end of this 
wire through the hole punched near the end of the 
coil tube next to the panel and connect this wire 
to the back of the binding post V 7 , Fig. 47 and Fig. 
48. The wire F, Fig. 48, is now connected to the 
back of the binding post Q. There now remain 
five twisted taps and one wire to be connected to 
the six switch contacts. The taps should be cut off 
about 1% inches from the coil tube, and the insula- 


222 


RADIO 


tion removed from the pairs of wires thus 
formed. Each pair of wires should be twisted 
together, as shown at J, Fig. 48. The connections 
are now made by clamping the five taps, and also 
the end of the single wire between the nuts and 
washers on the contact bolts. The connections 
are clearly shown in the diagram. 

We are now ready to assemble and wire the 
fixed portion of the coupler, composed of the base 
B, coil support J, panel K, and coil tube P. 

Screw the panel to the base and to the support 
J, and insert the binding posts, switch arms and 
bolts and contact bolts in the proper holes. The 
switch arms should now be adjusted so that they 
make firm contact on the heads of the contact 
bolts. Now insert four small screws E, Fig. 47, 
in the front of the panel, so that the switch arms 
will not drop off the row of contact points when 
the knobs are turned too far. Insert a wire be¬ 
tween the nuts on the end of the lower switch arm 
bolt N, where it projects through the back of the 
panel K, Fig. 47. Wind the wire into a spiral of 
one or two turns like a clock spring and connect 
the end to the upper binding post which is marked 
“antenna.” These connections will be under¬ 
stood by referring to the upper left-hand corner 
of Fig. 48. 


HOW TO BUILD A RECEIVER 223 

In the same manner connect another wire from 
the npper switch arm bolt to the lower binding 
post which is marked “ground.” See Fig. 48. 
The connecting wires should be insulated except 
where a connection is needed and should not touch 
each other. Two short pieces of wire are now 
fastened to the binding posts in the front of thQ 
panel, as previously explained. 

The coil tube P should now be laid on the base 
in about the same position as it is shown in Fig. 
47. The sixteen twisted taps and also the two 
single wires from the ends of the winding are now 
to be connected to the back of the eighteen con¬ 
tacts on the panel K. Scrape the cotton insulation 
from the loop ends of the sixteen twisted taps as 
well as from the ends of the two single wire taps 
coming from the first and last turns. Fasten the 
bare ends of these wires to the proper switch con¬ 
tacts. Be careful not to cut or break any of the 
looped taps. The connecting wires may be fas¬ 
tened to the switch contacts by binding them be¬ 
tween the washer and the nut. The order of 
connecting the taps may be understood by refer¬ 
ring to Fig. 48. 

Carefully raise the coil tube P against the sup¬ 
port J, to such a position that when the coil S, 
of the movable section of the tuner, is pushed in 



224 


BADIO 


the coil tube P, the space between the two tubes 
will be the same all around. Mark this position 
on the coil tube P on J and fasten it to J, with 
short wood screws. 

Wiring Condenser and Detector .— 

The mounting of the condenser C, and the crystal 
detector D, on the base B, is clearly shown in Fig. 
47. A wire is run from the binding post Y, on the 
variable condenser C, through a small hole in the 
base B, and is then connected to the under side of 
the detector binding post. Another wire is now 
run from the clip which holds the galena crystal 
through a small hole in the base, and is then con¬ 
nected to the under side of the right hand binding 
post IT. The left hand binding post U is next 
connected to the binding post on the variable con¬ 
denser, which has no wire attached to it, by run¬ 
ning a wire under the base and up through a small 
hole. The wiring will be understood by referring 
to the right hand portion of Fig. 48. The wires 
may be the same size as were used for winding 
the tubes and should be insulated. Two pieces 
of wire should now be connected from the binding 
posts W and Q, Fig. 47 and Fig. 48, to binding 
posts on the variable condenser. The telephone 
receivers T are now connected to the binding 


HOW TO BUILD A RECEIVER 225 

posts U and receiving set is complete, except for 
connecting to the antenna and ground. 

Connect the antenna lead and ground wire 
to the binding posts marked “antenna” and 
“ground,” with proper connections to antenna 
and ground. You are ready to operate your 
apparatus. Too much importance cannot be paid 
to a good ground connection. The lead should be 
as short as possible between the receiver and 
ground. 

Directions for Operating .—Push the 
coils S (secondary) about half way into the coil 
tube P (primary) and set the switch 2 on contact 
point 4. The primary switch 4 may be left in any 
position. The wire spring which rests on the 
crystal detector must be placed lightly at differ¬ 
ent points on the crystal until the transmitting 
station is heard. Then the set is adjusted as 
described below. During this operation contact 
switch should be placed on contact point 8. 

Having adjusted the crystal detector to a sensi¬ 
tive point, the next thing is to adjust the switches 
on the coil tube P (primary), the switch on the coil 
tube S (secondary) and also the variable con¬ 
denser C, so that the apparatus will be in reso¬ 
nance with the transmitting station. Set the 
primary switch N on contact point 1, and while 



226 


RADIO 


keeping it in this position move the other primary 
switch 0 over all of its contacts, stopping a mo¬ 
ment at each one. Care must be taken to see that 
the ends of the switch arms are not allowed to 
rest so that they will touch more than one contact 
point at a time. If no signals are heard, set the 
switch arm N on contact point No. 2 and again 
move the switch arm 0 over all of its contacts. 
Proceed in this manner until the transmitting sta¬ 
tion is heard. This is called “tuning” the pri¬ 
mary circuit. 

The tuning of the secondary circuit is the next 
operation. Set the secondary switch Z on con¬ 
tact 1, and turn the knob of the variable con¬ 
denser C so that the pointer moves over the entire 
scale. If no signals are heard set the switch on 
contact 2 and again turn the knob of the variable 
condenser so that the pointer moves over the 
entire scale. Proceed in this manner until the 
signals are loudest, being careful to see that the 
ends of the switch arms touch only one contact 
point at one time. Next slide the tube coil S (sec¬ 
ondary) in and out of the coil tube P (primary) 
until the signals are made as loud as possible. 
This operation is called changing the ‘ ‘ coupling. ’ ’ 
When the coupling which gives the loudest signal 
has been secured, it may be necessary to readjust 


HOW TO BUILD A RECEIVER 227 


slightly the position of the switch arm 0, the posi¬ 
tion of the movable coil tube S and the “setting’’ 
of the variable condenser C. 

The receiving set is now in resonance with the 
transmitting station. It is possible to change the 
position of one or more of the switch arms, the 
position of the movable coil tube and the setting 
of the variable condenser in such a manner that 
the set will be in resonance with the same trans¬ 
mitting station. In other words, there are dif¬ 
ferent combinations of adjustments which will 
respond to signals from the same transmitting 
station. The best adjustment is that which 
reduces the signals from undesired stations to a 
minimum and still permits the desired transmit¬ 
ting station to be heard. This is accomplished by 
decreasing the coupling (drawing coil tube S 
further out of coil tube P) and again tuning with 
the switch arm 0 and the variable condenser C. 
This may also weaken the signals from the de¬ 
sired transmitting station, but it will weaken the 
signals from the undesired stations to a greater 
extent, provided that the transmitting station it 
is desired to hear has a wave frequency which is 

not exactlv the same as that of the other stations. 
%/ 

This feature is called “selectivity.” 


APPENDIX I 


FIRE PROTECTION REGULATIONS 

Below will be found the latest regulations 
adopted by the National Board of Fire Under¬ 
writers. Readers installing radio equipments 
would do well to follow these regulations care¬ 
fully as any delinquency would cause an increase 
in the fire insurance rates, or a cancellation of 
existing policy. In some cities these regulations 
are made compulsory by the city regulations cov¬ 
ering fire protection. 

The entire list follows: 

All radio installations for Transmitting sta¬ 
tions and all Receiving installations having out¬ 
side exposed aerial lines (antenna) for receiving, 
or having connection with a light or power circuit 
should be approved by certificate from the Board 
of Fire Underwriters. 

In setting up radio equipment all wiring per¬ 
taining thereto must conform to the general re¬ 
quirements of the National Electrical Code for 
the class of work installed and the following addi¬ 
tional specifications. 


228 


APPENDICES 


229 


For Receiving Stations Only 
Antenna: 

(a) Antenna outside of buildings shall not 
cross over or under electric light or power wires 
of any circuit of more than 600 volts, or railway 
or trolley or feeder wires, nor shall they be so 
located that a failure of either antenna or of the 
above mentioned electric light or power wires can 
result in a contact between the antenna and such 
electric light or power wires. Antennae shall be 
so constructed and installed in a strong and dur¬ 
able manner and shall be so located as to prevent 
accidental contact with light and power wires by 
sagging or swinging. Splices and joints in the 
antenna span, unless made with proved clamps 
or splicing devices, shall be soldered. Antennae 
installed inside of buildings are not covered by 
the above specifications. 

Lead-in TVives: 

(b) Lead-in wires shall be of copper, approved 
copper-clad steel or other approved metal which 
will not corrode excessively and in no case shall 
they be smaller than No. 14 B. & S. gauge, except 
that approved copper-clad steel not less than No. 
17 B. & S. gauge may be used. 


230 


APPENDICES 


Lead-in wires on the outside of buildings shall 
not come nearer than four (4) inches to electric 
light and power wires, unless separated there¬ 
from by a continuous and firmly fixed non-con¬ 
ductor that will maintain permanent separation. 
The non-conductor shall be in addition to any 
insulation on the wire. 

Lead-in wires shal enter the building through 
a non-combustible, non-absorptive insulating 
bushing. 

Protective Device: 

(c) Each lead-in wire shall be provided with 
an approved protective device properly connected 
and located (inside or outside the building) as 
near as practicable to the point where the wire 
enters the building. The protector shall not be 
placed in the immediate vicinity of easily ignitable 
stuff, or where exposed to inflammable gases or 
dust, or flyings of combustible materials. The 
protective device shall be an approved lightning 
arrester which will operate at a potential of five 
hundred (500) volts or less. 

The use of an antenna ground switch is desir¬ 
able, but does not obviate the necessity for the 
approved protective device required in this sec¬ 
tion. The antenna grounding switch, if installed, 


APPENDICES 231 

shall, in its closed position, form a shunt around 
the protective device. 

Protective Ground TVire: 

(d) The ground wire may be bare or insulated 
and shall be of copper or approved copper-clad 
steel. If of copper the ground wire shall be not 
smaller than No. 14 B. & S. gauge; if of approved 
copper-clad steel, it shall be not smaller than No. 
17 B. & S. gauge. The ground wire shall be run 
in as straight a line as possible to a good, per¬ 
manent ground. Preference shall be given to 
water piping. Gas piping shall not be used for 
grounding protective devices. Other permissible 
grounds are grounded steel frames of buildings 
or other grounded metallic work in the building 
and artificial grounds such as driven pipes, plates, 
cones, etc. The ground wire shall be protected 
against mechanical injury, and an approved 
ground clamp shall be used wherever the ground 
wire is connected to pipes or piping. 

Wires Inside JBnilding: 

(e) Wires inside buildings shall be securely 
fastened in a workmanlike manner and shall not 
come nearer than two (2) inches to any electric 
light or power wire unless separated therefrom 
by some continuous and firmly fixed non-con- 


232 APPENDICES 

ductor making a permanent separation. This 
non-conductor shall be in addition to any regular 
insulation on the wire. Porcelain tubing or ap¬ 
proved flexible tubing may be used for encasing 
wires to comply with this rule. 

Receiving Equipment Ground Wire: 

(f) The ground conductor may be bare or 
insulated and shall be of copper, approved cop¬ 
per-clad steel, or other approved metal which will 
not corrode excessively under existing conditions, 
and in no case shall the ground wire be less than 
No. 14 B. & S. gauge, except that approved cop¬ 
per-clad steel, not less than No. 17 B. & S. gauge 
may be used. The ground wire may be run inside 
or outside the building, when receiving equipment 
ground wire is run in compliance with rules for 
protective ground wire; in Section (d) it may be 
used as the ground conductor for protective 
device. 


For Transmitting Stations 

Transmitting stations are regarded as involv¬ 
ing more hazard than stations used for only 
receiving, and require additional safeguard. All 
wiring and apparatus supplying power for send¬ 
ing, should be installed in accordance with the 


APPENDICES 


233 


National Electrical Code. Plans and specifica¬ 
tions for proposed transmitting stations should 
be submitted for approval in advance of installa¬ 
tion. 


APPENDIX II 


UNITED STATES AND INTERNATIONAL 
RADIO REGULATIONS 

Below are given extracts from the laws and 
regulations governing radio communications, as 
they apply to the experimenter and amateur. 

As will be seen, both an operator’s license and 
a station license is required to operate a trans¬ 
mitting station of any kind. However, no license 
is required to operate a receiving station only, 
except that the regulation regarding the secrecy 
of messages must be complied with. 

The regulations quoted apply to experimental 
and amateur stations and operators only. For 
regulations for commercial stations and opera¬ 
tors, application should be made to the Superin¬ 
tendent of Documents, Government Printing 
Office, Washington, D. C., for a book entitled 
“ Radio Communication Laws of the United 
States,” which covers the entire field of radio. 

Amateur and Experimental Station.— 
No private or commercial station not engaged 
in the transaction of bona fide commercial busi¬ 
ness by radio communication or in experimenta- 

234 


APPENDICES 


235 


tion in connection with the development and 
manufacture of radio apparatus for commercial 
purposes shall use a transmitting wave length 
exceeding two hundred meters, or a transformer 
input exceeding one kilowatt. 

The Secretary of Commerce may grant special 
temporary licenses to stations actually engaged 
in conducting experiments for the development of 
the science of radio communication, or the appa¬ 
ratus pertaining thereto, to carry on special tests, 
using any amount of power or any wave lengths, 
at such hours and under such conditions as will 
insure the least interference with the sending or 
receipt of commercial or Government radiograms, 
of distress signals and radiograms, or with the 
work of other stations. 

Station licenses for the use and operation of 
apparatus for radio communication under the act 
may be issued only to citizens of the United States 
or Porto Rico or to a company incorporated under 
the laws of some State or Territory or of the 
United States or Porto Rico. 

Licenses can be issued to clubs if they are incor¬ 
porated or if a member will accept the responsi¬ 
bility for the operation of the apparatus, carrying 
with it the possibility of being penalized for 
infraction of the laws. 


236 


APPENDICES 


Applications for station licenses of all classes 
should be addressed to the United States Radio 
Inspector for the district in which the station is 
located, who will forward the necessary blank 
forms and information. The limits of the dis¬ 
tricts and addresses of radio inspectors are given 
below. 

Upon receipt of the forms, properly completed, 
the radio inspector will make a thorough inspec¬ 
tion of the station if practicable. 

When applications and forms have been prop¬ 
erly submitted, the stations may be operated in 
accordance with the laws and regulations govern¬ 
ing the class of station for which application for 
license has been made, until such time as the appli¬ 
cation can be acted upon unless the applicant is 
otherwise instructed and provided temporary 
official call letters are assigned. 

General and restricted amateur-station licenses 
are issued directly by radio inspectors. Station 
licenses of all other classes are issued from the 
office of the Commissioner of Navigation, Depart¬ 
ment of Commerce. Applications and form are 
forwarded by radio inspectors with recommenda¬ 
tions by them. 

The owner of an amateur station may operate 
his station in accordance with the laws if his ap- 


APPENDICES 237 

plication for a license has been properly filed but 
has not been acted upon. An application for an 
operator’s license must also have been filed and 
every effort made to obtain the license before the 
station may be operated. 

‘‘Provisional” station licenses are issued to 
amateurs remote from the headquarters of the 
radio inspector of the district in which the station 
is located. These licenses are issued as a matter 
of convenience and record. If, upon inspection, 
the station is found to comply with the law, th.e 
inspector will strike out the word “Provisional” 
and insert the date of inspection and his signa¬ 
ture at the bottom of the license. 

If such a station is found not to comply with 
the law the provisional license may be canceled 
until such time as the apparatus is readjusted to 
meet the requirements of the law: Provided, how¬ 
ever, That consideration will be given to any 
reports of interference filed against such a sta¬ 
tion. 

All persons are warned that it is unlawful to 
operate stations after licenses have expired un¬ 
less application for renewal has been properly 
made. 

Hereafter expired station licenses of all classes, 
commercial and amateur, need not be returned to 


238 


APPENDICES 


the radio inspectors with applications for re¬ 
newals. Owners desiring a renewal license must 
complete new forms, as prescribed for original 
applications. New licenses will be issued in every 
case of renewal. 

Any person applying for a duplicate license to 
replace an original which has been lost, mutilated, 
or destroyed will be required to submit an affi¬ 
davit to the Bureau of Navigation through the 
radio inspector of the district, attesting the facts 
regarding the manner in which the original was 
lost. The Commissioner of Navigation will con¬ 
sider the facts in the case and advise the radio 
inspector in regard to the issue of a duplicate 
license, or a duplicate will be forwarded through 
the inspector’s office. 

A duplicate license will be issued under the 
same serial number as the original and will be 
marked “Duplicate” in red across the face. 

Decrement of Stations .—At all stations 
if the sending apparatus, to be referred to here¬ 
inafter as the “transmitter,” is of such a charac¬ 
ter that the energy is radiated in two or more wave 
lengths, more or less sharply defined, as indicated 
by a sensitive wavemeter, the energy in no one of 
the lesser waves shall exceed ten per centum of 
that in the greatest. 


APPENDICES 


239 


At all stations the logarithmic decrement per 
complete oscillation in the wave trains emitted by 
the transmitter shall not exceed two-tenths, 
except when sending distress signals or signals 
and messages relating thereto. 

Interferences and Fraudulent Sig¬ 
nals .—That every license granted under the 
provisions of this Act for the operation or use of 
apparatus for radio communication shall pre¬ 
scribe that the operator thereof shall not willfully 
or maliciously interfere with any other radio com¬ 
munication. Such interference shall be deemed 
a misdemeanor, and upon conviction thereof the 
owner or operator, or both, shall be punishable 
by a fine of not to exceed five hundred dollars or 
imprisonment for not to, exceed one year, or both. 

That the expression “radio communication” 
as used in this Act means any system of electrical 
communication by telegraphy or telephony with¬ 
out the aid of any wire connecting the points from 
and at which the radiograms, signals, or other 
communications are sent or received. 

That a person, company, or corporation within 
the jurisdiction of the United States shall not 
knowingly utter or transmit, or cause to be 
uttered or transmitted, any false or fraudulent 


240 


EADIO 


distress signal or call or false or fraudulent sig¬ 
nal, call, or other radiogram of any kind. For 
sending out such fraudulent signals the penalty is 
a fine not exceeding $2,500 or five years ’ imprison¬ 
ment, or both. 

Secrecy of Signals .—No person or persons 
engaged in or having knowledge of the operation 
of any station or stations, shall divulge or publish 
the contents of any messages transmitted or 
received by such station, except to the person or 
persons to whom the same may be directed, or 
their authorized agent, or to another station 
employed to forward such message to its destina¬ 
tion, unless legally required so to do by the court 
of competent jurisdiction or other competent 
authority. Any person guilty of divulging or 
publishing any message, except as herein pro¬ 
vided, shall, on conviction thereof, be punished by 
a fine of not more than two hundred and fifty 
dollars or imprisonment for a period of not ex¬ 
ceeding three months, or both fine and imprison¬ 
ment, in the discretion of the court. 

Requirements for Operators, Licenses 

Experiment and Instruction Grade.— 

Experimenters and instructors of scientific attain¬ 
ments in the art of radio communication whose 


APPENDICES 241 

knowledge of the radio laws satisfies the radio in¬ 
spector or the examining officer may obtain this 
grade license, provided they are able to transmit 
and receive in the Continental Morse Code at a 
speed sufficient to enable them to recognize dis¬ 
tress calls or the “keep-out” signals. 

The operator’s license for this grade is a com¬ 
mercial license, indorsed by the Secretary of Com¬ 
merce with a statement of the special purpose for 
which it is valid. 

If the applicant qualifies, the radio inspector or 
examining officer will forward a blank commercial 
license, with the papers, to the Commissioner of 
Navigation, with his recommendation. If ap¬ 
proved, the license will be properly indorsed by 
the Secretary of Commerce and delivered to the 
licensee through the recommending officer. 

This license has no reference to the instruction 
of radio operators as such, but is required by 
those operating apparatus licensed as experi¬ 
mental stations but who are unable to obtain com¬ 
mercial grade operators’ licenses. 

Amateurs before applying for licenses should 
read and understand the essential parts of the 
International Radiotelegraphic Convention in 
force and sections 3, 4, 5, and 7 of the act of 
August 13,1912. The Department recognizes that 


242 


APPENDICES 


radio communication offers a wholesome form of 
instructive recreation for amateurs. At the same 
time its use for this purpose must observe strictly 
the rights of others to the uninterrupted use of 
apparatus for important public and commercial 
purposes. The Department will not knowingly 
issue a license to an amateur who does not recog¬ 
nize and will not obey this principle. To this end 
the intelligent reading of the International Con¬ 
vention and the act of Congress is prescribed as 
the first step to be taken by amateurs. A copy of 
the radio laws and regulations may be procured 
for this purpose from the radio inspectors or 
from the Commissioner of Navigation, Depart¬ 
ment of Commerce, Washington, D. C., but they 
are not for public distribution. Additional copies 
may be purchased from the Superintendent of 
Documents, Government Printing Office, Wash¬ 
ington, D. C., at a nominal price. 

Amateur First Grade .—The applicant 
must have a sufficient knowledge of the adjust¬ 
ment and operation of the apparatus which he 
wishes to operate and of the regulations of the In¬ 
ternational Convention and acts of Congress in so 
far as they relate to interference with other radio 
communication and impose certain duties on all 
grades of operators. The applicant must be able 


APPENDICES 243 

to transmit and receive in Continental Morse at a 
speed sufficient to enable him to recognize distress 
calls or the official “keep-out” signals. A speed 
of at least 10 words per minute (five letters to the 
word) must be attained. 

A.matenr second grade .— The require* 
ments for the second grade will be the same as for 
the first grade. The second-grade license will be 
issued only where an applicant can not be per¬ 
sonally examined or until he can be examined. 
An examining officer or radio inspector is author¬ 
ized in his discretion to waive an actual examina¬ 
tion of an applicant for an amateur license, if the 
amateur for adequate reasons can not present 
himself for examination but in writing can satisfy 
the examining officer or radio inspector that he is 
qualified to hold a license and will conform to its 
obligations. 

Amateurs should write to the nearest examining 
officer in their vicinity for Form 756 “Application 
for operator’s license,” and to the radio inspector 
in their vicinity for Form 762 “Amateur appli¬ 
cant’s description of apparatus.” 

Foreign-born applicants for station licenses 
must submit satisfactory evidence of their citizen¬ 
ship. 

Amateur operators at points remote from 


244 


APPENDICES 


examining officers and radio inspectors may be 
issued second-grade amateur licenses without 
personal examination. Examinations for first- 
grade licenses will be given by the radio inspector 
when he is in that vicinity, but special trips can 
not be made for this purpose. (See par. 123.) 

Persons holding radio operators ’ licenses, ama¬ 
teur second grade, should make every effort to 
appear at one of the examination points to take 
the examination for amateur first-grade license or 
higher. 

Persons holding radio operators ’ licenses of 
any grade should, before their licenses expire, 
apply to the nearest radio inspector or examining 
officer for renewal and submit Form 756 in dupli¬ 
cate. 

Operators’ licenses are not valid until the oath 
for the preservation of the secrecy of messages is 
properly executed before a notary public or other 
officer duly authorized to administer oaths. 
Licenses must indicate on their faces that the 
oath has been taken and the officer administering 
the oath on the back of the license should sign 
also in the blank provided on the face. 

Licenses will not be signed by examining officers 
until the oath of secrecy has been properly 
executed. 


APPENDICES 


245 


Administration and Administrative 

Districts: 

The Department has established, for the pur¬ 
pose of enforcing, through radio inspectors and 
others, the acts relating to radio communication 
and the International Convention, the following 
districts, with the principal office for each district 
at the customhouse of the port named. 

All information regarding operators and sta¬ 
tion licenses may be obtained from Radio Inspec¬ 
tors at the addresses below. 

Communications for radio inspectors should 
be addressed as follows, and not to individuals: 

Radio Inspector, Customhouse,- (city) - 

(State). 

Communications for the Bureau of Navigation 
should be addressed as follows, and not to indi¬ 
viduals: Commissioner of Navigation, Depart¬ 
ment of Commerce, Washington, D. C. 

1. Boston, Mass. : Maine, New Hampshire, Ver¬ 

mont, Massachusetts, Rhode Island, Con¬ 
necticut. 

2. New York, N. Y.: New York (county of New 

York, Staten Island, Long Island, and coun¬ 
ties on the Hudson River to and including 
Schenectady, Albany, and Rensselaer) and 




246 


APPENDICES 


New Jersey (counties of Bergen, Passaic, 
Essex, Union, Middlesex, Monmouth, Hud¬ 
son, and Ocean). 

3. Baltimore, Md.: New Jersey (all counties not 

included in second district), Pennsylvania 
(counties of Philadelphia, Delaware, all coun¬ 
ties south of the Blue Mountains, and Frank¬ 
lin County), Delaware, Maryland, Virginia, 
District of Columbia. 

4. Savannah, Ga. : North Carolina, South Caro¬ 

lina, Georgia, Florida, Porto Rico. 

5. New Orleans, La.: Alabama, Mississippi, 

Louisiana, Texas, Tennessee, Arkansas, Okla¬ 
homa, New Mexico. 

6. San Francisco, Calif.: California, Hawaii, 

Nevada, Utah, Arizona. 

7. Seattle, Wash.: Oregon, Washington, Alaska, 

Idaho, Montana, Wyoming. 

8. Cleveland, Ohio: New York (all counties not 

included in second district). Pennsylvania 
(all counties not included in third district), 
West Virginia, Ohio, Michigan (Lower Pen¬ 
insula). 

9. Chicago, III. : Indiana, Illinois, Wisconsin, 

Michigan (Upper Peninsula), Minnesota, 
Kentucky, Missouri, Kansas, Colorado, Iowa, 
Nebraska, South Dakota, North Dakota. 


APPENDICES 


247 


lOTutuTiom Mwomiawaio nonaroi 

UST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION 


MBfttVW 

TtON 


PBB 

QRA 

ORB 

OBC 

QBD 

QRF 

QKO 

QRB 

ou 

QRK 

QBL 


OBM 

QRN 

QRO 

QRP 

ORQ 

ORS 

ORT 

QRU 

QRV 

ORW 

ORX 

-ORY 

QRZ 

OSA 

OSB 

OSC 

OSD 

OSF 

osa 

OSH 

OSJ 

QSK 

OSL 

OSM 

OSN 

QSO 

OSP 

OSQ 

OSB 

OST 

Q8U 

•OST 

08W 

08X 

OST 

OS* 

OTA 


QUESTION. 


MSWCB Ol NOTICE. 


Do you wish to communicate b j means of the 
International Signal Code! 

What ship or coast station.Is that!. 

What Is your distanceT... 

What Is your true bearing!. 

Where are you bound fort... 

Where aro you bound from!. 

What Hue do you belong tot........ 

What is your wave length In metcrq.1. 

How many words have you tp send!... 

How do ypu receive met.,. 

'Are you receiving badlyt Shall I send 201. 

• • • ■■ • 

for adjustment!. 

Are you bfctng Interfered with!.. 

Are the atmospherics strong!....... 

Shell I Increase power!.. .. 

Shall I decrease power!.... 

Shall I send faster!. 

Shall I send slower!...'.. 

Shall I stop sendingt... 

Have you anything for me!....... 

Are you ready!...,... 

Are you busy!. 


Shall I stand by!...... 

When wiU- be my turnt. . . 

Are my signals weak!. 

Are my signals strong!.... 

Is my toqo bad!...... 

Is my spark bad!.:.... 

Is my spacing, bad!.... 

What Is your time!...t.............— 

Is transmission to be [n alternate order or In 
series! 


What rateeb'eJl I collect for-1.. 

Is the lost radiogram canceled!... 

Did you get my receipt!.. 

What is your true course!.. 

Are you In communication with land!. 

Are you in communication with any ship or 

station (ore with..)! 

Shall I inform....that you are calling Rim T 

Is.calling roe!..... 

Will you forward the radiogram?.. 

Hare you received the general call!. 

please call me when you have finished (or: at 
_o’clock)! 

la public correspondence being handled I. -- — 


Shall I Increase my spark frequency!. 

Shall I decrease my epark frequency!. 

Shall I send on a wave length of.meters! 


I wish to communicate by meansol the Inte> 
national Signal Code. 

This U.. 

My distance le.. 

My true bearing Is.,.degrees. 

I am bound for. 

I am bound from—. 

1 belong to the........Line. 

My wave length Is.meter*. 

1 have.word* to send. 

I am receiving well. 

I am receiving badly. Please stud 8% 

• • • mm ' 
for adjustment. 

-I am being Interfered with. 

Atmospherics are very strong, 
increase power. 

Decrease power. 

Send faster. 

Send slower. 

Stop sending. 

1 have nothing for you. 

I am ready. All right pow. 

I am busy (or: I am busy with.). 

do not Interfere. 

Stand by. I will cad you phen required. 

Your turn will be No.. 

Your signals are weak. 

Your signals are strong; 

The tone Is had. 

The spark Is bad. 

Your spaelng Is bad. 

My time Is. 

Transmission will be In alternate order* 


Transmission will be in sarles of 5 messages. 
Transmission will be In aerie* of 10 messages. 

Collect., 

Tbe last radiogram le caqeeted. 

Please acknowledge. 

My true course Is.degrees. 

1 am not In communication with land. 

I am In communication with.. .(through 

.). 

Inform....that I am calling him. 

You are being colled by. 

I will forward the rtullogram. 

General call tp all stations. 

Will call when 1 bare finished. 

Public correspondence Is being nandle^ 
Please do not Interfere. 

Increase your spark frequency. 

Decrease your spark frequency. 

Let us change to tbe wave length of—...... 

meters. 

Send each word twice. 1 hare difficulty ID 
receiving you. 

Repeat the last radiogram. 


•EuWlc correspondence Is any radio work, official or private,-bandied on commercial wave length! 
When an abbrevl&lpn It followed by a mark pf interrogation, Jt refers to the question indicated 
to ^abbreviation. 





































































248 


APPENDICES 


INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS 

To b« wed let *11 general public aeirice radio communication 

/ , 

t A dash Ir eqo&l to three dots. t. The space betweep two letters la oaual to 

The space between parts of the same Utter three dots. 

U -equal to one doc A The space between two words U eqoal. to 

five data 
































V 


BIBLIOGRAPHY 


APPENDIX B 
Bibliography 

The following list of publications relating to the art of 
radio was prepared by the United States Bureau of 
Standards. While it is by no means comprehensive, ai 
few of the most important references are given for each 
of the subjects mentioned. 

The reader may also obtain from the Superintendent 
of Public Documents, Government Printing Office, 
Washington, D. C., a list of books bearing upon radio, 
together with their prices. Many excellent works upon 
the subject are available from this source, at exceed¬ 
ingly moderate prices. 

From the same office may be obtained laws and regula¬ 
tions relating to radio, also a complete list of stations, 
both ship and shore, including broadcasting telephone 
stations:— 

ELEMENTARY ELECTRICITY 

1. Elements of Electricity and Magnetism, J. J. Thom¬ 

son; 4th ed., 1909 (Cambridge). 

2. Modern Views of Electricity, 0. J. Lodge; 1889 

(Macmillan). 

3. The Elements of Physics, Vol. II, Electricity and 

Magnetism, Nichols and Franklin; 1905 (Mac¬ 
millan). 

4. Electricity and Magnetism, It. T. Glazebrook; 1910 

(Cambridge). 

5. Elements of Electricity for Technical Students, 

W. H. Timbie; 1911 (John Wiley & Sons). 

251 


252 APPENDICES 

6. Magnetism and Electricity for Students, H. E. Had¬ 

ley; 1910 (Macmillan). 

7. The Elements of Electricity and Magnetism, Frank¬ 

lin and MacNut; 1914 (Macmillan). 

8. Elementary Lessons in Electricity and Magnetism, 

S. P. Thompson; 7th ed , 1915 (Macmillan). 

‘9. A Treatise on Electricity, F. B. Pidduck; 1916 
(Cambridge). 

9a. Electricity and Magnetism, S. G. Starling; 1912 
(Longmans, Green & Co.). 

ALTERNATING CURRENTS 

11. Alternating Currents, Bedell and Crehore; 4th ed., 

1901 (McGraw-Hill). 

12. Alternating Currents and Alternating Current 

Machinery, D. C. and J. P. Jackson; 1896 (Mac¬ 
millan)^ 

13. The Theory of Alternating Currents (2 vols.), A. 

Russell; 2d ed., 1914 (Cambridge). 

14. Kapazitat und Induktivitat, E. Orlich; 1909. 

15. Calculation of Alternating Current Problems, L. 

Cohen; 1913 (McGraw-Hill). 

16. The Foundations of Alternating Current Theory, 

C. V. Drysdale; 1910 (E. Arnold). 

17. Transient Electric Phenomena and Oscillations, 

C. P. Steinmetz; 1909 (McGraw-Hill). 

COUPLED CIRCUITS 

21. Currents in Coupled Circuits; A. Oberbeck; Anna- 

len der Physik, 291, p. 623; 1895. 

22. Use of Coupled Circuits; F. Braun; Physikalische 

Zs., 3, p. 148; 1901. 


APPENDICES 253 

23. Coupling phenomena; M. Wien; Annalen der Phy- 

sik, 61, p. 151, 1897; 25, p. 1, 1908. 

24. Maximum Current in the Secondary of a Trans¬ 

former; J. S. Stone; Physical Review, 32, p. 399; 
1911. 

25. Cisoidal Oscillations; G. A. Campbell; Trans. A. I. 

E. E., 30, p. 873; 1911. 

26. The Impedances, Angular Velocities, and Frequen¬ 

cies of Oscillating-Current Circuits; A. E. Ken- 
nelly ; Proc. I. R. E. 4, p. 47; 1916. 

27. Alternating and Transient Currents in Coupled 

Electrical Circuits; F. E. Pernot; University of 
California, publications in Engineering, 1, p. 161; 
1916. 

28. Oscillograph Demonstrations of Coupled Circuits; 

G. W. O. Howe; Proc. Physical Society London, 
23, p. 237; 1911. J. A. Fleming; Proc. Physical 
Society London, 25, p. 217, 1913. 

29. Mechanical Models; T. R. Lyle; Phil. Mag., 25, p. 

567; 1913. W. Deutsch; Physikalische Zs., 16, 
p. 138; 1915. 


ANTENNA CALCULATIONS 

31. Theory of Horizontal Antennas; J. S. Stone; Trans. 

Int. Elec. Congress, St. Louis, 3, p. 555; 1904. 

32. Theory of Loaded Antenna; A. Guyau; La Lumiere 

Electrique, 15, p. 13; 1911. 

33. Capacity of Radiotelegraphic Antennas; G. W. 0. 

Howe; Electrician, 73, pp. 829, 859, 906, 1914; 75, 
p. 870; 1915. 

34. The Electrical Constants of Antennas; L. Cohen; 

Elec. World, 65, p. 286; 1915. 


254 


APPENDICES 


DAMPING 

41. Theory of Free Oscillations; Alternating Current 

Phenomena, C. P. Steinmetz; Appendix II, p. 
709; 4th ed., 1908. 

42. Decrements in Coupled Circuits; Y. Bjerknes; 

Annalen der Physik, 44, pp. 74, 92, 1891; 291, p. 
121, 1895. M. Wien, Annalen der Physik, 25, p. 
625, 1908; 29, p. 679, 1909. 

43. Linear Decrement: J. S. Stone; Electrician, 73, p. 

926; 1914. Proc. I. R. E., 2, p. 307, 1914; 4, p. 
463, 1916. 


ELECTROMAGNETIC WAVES 

51. A Treatise on Electricity and Magnetism; J. C. 

Maxwell; 1873. 

52. Recent Researches in Electricity and Magnetism; 

J. J. Thomson; 1893. 

53. Electromagnetic Theory (3 vols.) ; O. Heaviside; 

1893. 

54. Signaling Through Space Without Wires; O. J. 

Lodge; 1894. 

55. Derivation of Equations of a Plane Electromagnetic 

Wave; E. B. Rosa; Phys. Rev., 8, p. 282; 1899. 

56. Electric Waves; H. Hertz (translated into English 

by D. E. Jones) ; 1900. 

57. Maxwell’s Theory and Wireless Telegraphy; H. 

Poincare (translated into English by F. K. Vree- 
land); 1904. 

58. Researches in Radiotelegraphy; J. A. Fleming; 

Smithsonian Report for 1909, p. 157. 


APPENDICES 


255 


RADIO MEASUREMENTS AND 
MISCELLANEOUS 

61. The Principles of Electric Wave Telegraphy and 

Telephony; J. A. Fleming; 3d ed., 1916. 

62. Les Oscillations Electriques; C. Tissot; 1910. 

63. Radiotelegraphisches Praktikum; H. Rein; 1912. 

64. Wireless Telegraphy; J. Zenneck (translated into 

- English by A. E. Seelig); 1915. 

65. Wireless Telegraphy and Telephony, A Handbook; 

W. H. Eccles; 1916. 

66. Radio Communication; J. Mills; 1917. 

67. Standardization Rules, Institute of Radio Engineers; 

1915. 


WAVE LENGTH 

71. Die Frequenzmesser und Dampfungsmesser der 

drahtlosen Telegraphie; E. Nesper; 1907. 

72. Standard Wave Length Circuits; A. Campbell; 

Phil. Mag., 18, p. 794; 1909. Electrician, 64, p. 
612; 1910. 

73. Calibration of Wavemeters; G. W. 0. Howe; Elec¬ 

trician, 69, p. 490; 1912. 

74. Wavemeter Standardization; Diesselhorst; Elektro- 

technische Zs., 29, p. 703; 1908. 

75. Pointer-Type Wavemeter; Ferrie and Carpentier; 

Jahrb. d. drahtl. Tel., 5, p. 106; 1911. 

76. Practical Uses of the Wavemeter in Wireless Teleg¬ 

raphy; J. O. Mauborgne; 1914. 

77. Oval Diagram for Wave Length Calculations; W. H. 

Eccles; Electrician, 76, p. 388; 1915. 



256 


APPENDICES 


CAPACITY 

81. Square-Plate Condenser for Uniform Scale of Wave 

Length; C. Tissot; Journal de Physique, 2; p. 719 ; 
1912. 

82. Rotary Condenser for Uniform Scale of Wave 

Length; W. Duddell; Jour. I. E. E., 52, p. 275; 
1914. 

83. A-c. Resistance of Condensers; Fleming and Dyke; 

Electrician, 68, pp. 1017, 1060, 1912; 69, p. 10; 
1912. G. E. Bairsto; Electrician, 76, p. 53; 1915. 

84. Calculation of Capacity Using Method of Images; 

“Alternating Currents”; A. Russell; Yol. 1, 
chaps. 5 and 6; 1914. 

INDUCTANCE 

91. The Effects of Distributed Capacity of Coils Used 

in Radiotelegraphic Circuits; F. A. Kolster; Proc. 

I. R. E., 1, p. 19; 1913. 

92. Distributed Capacity of Single-Layer Solenoids; 

J. C. Hubbard; Phys. Review, 9, p. 529; 1917. 

93. Development of Inductance Formulas; “Alternating 

Currents”; A. Russell; Yol. I, chaps. 2 and 3; 
1914. “Absolute Measurements in Electricity and 
Magnetism”; A. Gray; Yol. II, part 1, chap. 6. 

CURRENT MEASUREMENT 

101. Thermoelements for High-Frequency Measure¬ 

ments; Dowse; Electrician, 65, p. 765; 1910. 

102. Hot-Strip Ammeters for Large High-Frequency 

Currents; R. Hartmann-Kempf; Elektrotech- 
nische Zs., 32, p. 1134; 1911. G. Eichhorn; Jahr- 
buch d. drahtl. Tel., 5, p. 517; 1912. 


APPENDICES 257 

103. High-Frequency Current Transformer; Campbell 

and Dye; Proc. Royal Soc., 90, p. 621; 1914. 

104. Use of Iron in High-Frequency Current Trans¬ 

former; McLachlan; Electrician, 78, p. 382; 
1916. 

105. Use of Galvanometer in Audion Plate Circuit; L. E. 

Whittemore; Phys. Review, 9, p. 434; 1917. 

106. Measurement of Signal Intensity with Crystal De¬ 

tector; J. L. Hogan; (Marconi) Year-Book of 
Wireless Telegraphy, p. 662; 1916. 

107. Measurements With Crystal and Telephone; J. 

Zenneck; Proc. I. R. E., 4, p. 363; 1916. 

108. Current Measurement With the Audion; L. W. 

Austin; Jour. Wash. Acad. Sciences, 6, p. 81; 
1916. Proc. I. R. E., 4, p. 251; 1916. Electrician, 
78, p. 465 ; 1917. Proc. I. R. E., 5, p. 239; 1917. 

HIGH-FREQUENCY RESISTANCE 

111. Skin Effect in Round Wires; Lord Rayleigh; Phil. 

Mag., pp. 382, 469, 886; Sci. Papers, Yol. II, pp. 
486, 495. Skin Effect in Round Wires; Lord 
Kelvin; Math, and Phys. Papers, Vol. Ill, p. 491; 
1889. 

112. Skin Effect in Stranded Conductors to Oscillatory 

Currents; F. Dolezalek; Ann. der. Phys., (4), 
12, p. 1142; 1903. 

113. Passage of High-Frequency Current Through 

Coils; M. Wien; Ann. der Phys., (4), 14, p. 1; 
1904. 

114. Long Solenoids at High Frequencies, Mathematical 

Theory; A. Sommerfeld; Ann. der Phys., (4), 
15, p. 673, 1904; (4), 24, p. 609, 1907. 

115. Calorimetric Measurements of High-Frequency 


258 


APPENDICES 


Resistance of Solenoids; T. Black; Ann. der 
Phys., 19, p. 157; 1906. 

116. Measurements on Stranded Conductors; R. Linde- 

man; Verh. deutsch. Phys. Gesel., 11, p. 682; 
1909. 

117. Theory for Stranded-Conductor Solenoids; Moller; 

Ann. der Phys., 36, p. 738, 1911; and Jahr. draht. 
Tel., 9, p. 32, 1914. 

118. Measurements on Single and Multiple Layer Coils; 

Esau; Ann. der Phys., 34, p. 57; 1911. 

119. Skin Effect in Flat Coils and Short Cylindrical 

Coils; Lindemann and Huter; Verh. deutsch. 
Phys. Ges., 15, p. 219; 1913. 

120. The Alternating-Current Resistance of Long Coils 

of Stranded Wire, Theory; Rogowski; Arch. f. 
Elect., 3, p. 264; 1915. 

121. Bibliography, and Measurements on Wires and 

Strips; Kennelly, Laws, and Pierce; Proc. A. I. 
E. E., 34, p. 1749; 1915. 

122. Bibliography, and Measurements on Solid and 

Stranded Conductors; Kennedy and Affel; Proc. 
I. R. E., 4, p. 523; 1916. 

123. High-Frequency Resistance of Multiply-Stranded 

Insulated Wire; G. W. 0. Howe; Proc. Royal 
Society London, 93, p. 468; 1917. 

124. The Accuracy of High-Frequency Resistance Meas¬ 

urements; S. Loewe, Jahrbuch d. Drahtlosen 
Telegraphie, 7, p. 365; 1913. 

r 

ELECTRON TUBES 

131. Theory of Thermionic Emission; 0. W. Rich¬ 

ardson; Phil. Trans., 202, p. 516; 1903. 

132. Audion Detector and Amplifier; L. De Forest; 


APPENDICES 259 

Electrician, 73, p. 842; 1914. Elec. World, 65, 
p. 465; 1914. 

133. Theory of Electron Tubes; I. Langmuir; Phys. Re¬ 

view, 2, p. 450; 1913. Proc. I. R. E., 3, p. 261; 
1915. 

134. Operating Features of the Audion, Amplification, 

etc.; E. H. Armstrong; Elec. World, 64, p. 1149; 
1914. Proc. I. R. E., 3, p. 215, 1915; 5, p. 145; 
1917. 

135. Characteristic Curves, and Uses as Source of High 

Frequency Current; J. Bethenod; La Lumiere 
Electrique, 35, pp. 25, 225; 1916. 

136. Generalized Equations for Audions; M. Latour; La 

Lumiere Electrique, Dec. 30, 1916. Electrician, 
78, p. 280; 1916. 

137. Characteristics of Audion Tubes Used in Radio¬ 

telegraphy; G. Vallauri; L ’Elettrotecnica, 4, 
Nos. 3, 4, 18, and 19; 1917. 

138. Use of Pliotron to Produce Extreme Frequencies, 

Currents, and Voltages; W. C. White; General 
Electric Review, 19, p. 771,1916 ; 20, p. 635,1917. 

MISCELLANEOUS SOURCES OF HIGH- 
FREQUENCY CURRENT 

141. Disturbing Short Waves in Buzzer Circuits; S. 

Loewe; Jahrb. d. drahtl. Tel.. 6, p. 325; 1912. 

142. Production of Undamped Oscillations; M. Wien; 

Jahrb. d. drahtl. Tel., 1, p. 474; 1908. Physi- 
kalische Zs., 11, p. 76; 1910. 

143. Impulse Excitation Transmitter; E. W. Stone; 

Proc. I. R. E., 4, p. 233, 1916; 5, p. 133, 1917. 

144. Frequency Multipliers; A. N. Goldsmith; Proc. I. 

R. E., 3, p. 55; 1915. W. H. Eceles; Electrician, 
72, p. 944; 1914. 


260 APPENDICES 

145. High-Frequency Alternator of Induction Type; 

General Electric Review, 16, p. 16; 1913. 

146. High-Frequency Alternator Employing Rotating 

Magnetic Fields; R. Goldschmidt; Electrician, 
66, p. 744; 1911. T. R. Lyle; Electrician, 71, p. 
1004; 1913. 

147. Duddell Arc; W. Duddell; Jour. Rontgen Soc., 4, 

p. 1; 1907. 

148. Arc generator for laboratory purposes; F. Kock, 

Phys. Zeitschr., 12, p. 124; 1911. 

149. Impact excitation of undamped waves; E. L. Chaf¬ 

fee; Jahrb. d. drahtl. Tel. 7, p. 483; 1913. Proc. 
Amer. Ac. Arts and Sci, 47, No. 9; p. 267; 1911. 


PUBLICATIONS OF THE BUREAU OF STAND¬ 
ARDS BEARING ON RADIO MEASUREMENTS 

Units and Instruments 

151. Units of Weight and Measure; Circular No. 47; 

1914. 

152. Electric Units and Standards; Circular No. 60; 

1916. International System of Electric and 
Magnetic Units; J. H. Dellinger; Bull., 13, p. 
599; 1916 (S. P. 292). 

153. Electrical Measuring Instruments; Circular No. 20, 

2d ed., 1915. 

154. Fees for Electric, Magnetic, and Photometric 

Testing; Circular No. 6; 7th ed., 1916. 

ELECTRICAL PROPERTIES OF MATERIALS 

161. Copper Wire Tables; Circular No. 31; 3d ed., 1914. 

162. Electric Wire and Cable Terminology; Circular No. 

37; 2d ed., 1915. 


APPENDICES 261 

163. Insulating Properties of Solid Dielectrics; H. L. 
Curtis; Bull., 11, p. 359; 1914 (S. P. 234). 

CAPACITY AND INDUCTANCE 

171. The Testing and Properties of Electric Condensers; 

Circular No. 36; 1912. 

172. Formulas and Tables for the Calculation of Mutual 

and Self Inductance; Rosa and Grover; Bull., 8, 
p. 1; 1911 (S. P. 169). 

173. Various papers on inductance calculations; see Cir¬ 

cular No. 24, ‘ ‘ Publications of the Bureau of 
Standards . 99 

174. The Absolute Measurement of Capacity; Rosa and 

Grover; Bull., 1, p. 153; 1904 (S. P. 10). 

175. Measurement of Inductance by Anderson’s Method, 

Using Alternating Currents and a Vibration Gal¬ 
vanometer; Rosa and Grover; Bull., 1, p. 291; 
1905 (S. P. 14). 

176. The Simultaneous Measurement of the Capacity 

and Power Factor of Condensers; F. W. Grover, 
Bull., 3, p. 371; 1907 (S. P. 64). 

177. Mica Condenser as Standards of Capacity; H. L. 

Curtis, Bull., 6, p. 431; 1910 (S. P. 137). 

178. The Capacity and Phase Difference of Paraffined 

Paper Condensers as Functions of Temperature 
and Frequency; F. W. Grover; Bull., 7, p. 495; 
1911 (S. P. 166). 

179. The Measurement of the Inductances of Resistance 

Coils; Grover and Curtis; Bull., 8, p. 455; 1911 
(S. P. 175). 

180. Resistance Coils for Alternating Current Work; 

Curtis and Grover; Bull., 8, p. 495; 1911 (S. P. 
177). 


262 APPENDICES 

181. A Variable Self and Mutual Inductor; Brooks and 
Weaver; Bull., 13, p. 569; 1916 (S. P. 290). 

RADIO SUBJECTS 

191. The Influence of Frequency Upon the Self-Induc¬ 

tance of Coils; J. G. Coffin; Bull., 2, p. 275; 1906 
(S. P. 37). 

192. The Influence of Frequency on the Resistance and 

Inductance of Solenoidal Coils; L. Cohen; Bull., 

4, p. 161; 1907 (S. P. 76). 

193. The Theory of Coupled Circuits; L. Cohen; Bull., 

5, p. 511; 1909 (S. P. 112). 

194. Coupled Circuits in which the Secondary has Dis¬ 

tributed Inductance and Capacity; L. Cohen; 
Bull., 6, p. 247; 1909 (S. P. 126). 

195. High-Frequency Ammeters; J. H. Dellinger; Bull., 

10, p. 91; 1913 (S. P. 206). 

196. Direct-Reading Instrument for Measuring Loga¬ 

rithmic Decrement and Wave Length of Elec¬ 
tromagnetic Waves; F. A. Kolster; Bull., 11, 
p. 421; 1914 (S. P. 235). 

197. Effect of Imperfect Dielectrics in Field of Radio- 

telegraphic Antennas; J. M. Miller; Bull., 13, 
p. 129; 1916 (S. P. 269). 

PUBLICATIONS OF THE UNITED STATES 
NAVAL RADIOTELEGRAPHIC LABORA¬ 
TORY IN THE BULLETIN OF THE 
BUREAU OF STANDARDS 

201. Detector for Small Alternating Currents and Elec¬ 

trical Waves; L. W. Austin; Bull., 1, p. 435; 
1905 (S. P. 22). 

202. The Production of High-Frequency Oscillations 


APPENDICES 


263 


from the Electric Arc; L. W. Austin; Bull., 3, 
p. 325; 1907 (S. P. 60). 

203. Some Contact Rectifiers of Electric Currents; L. W. 

Austin; Bull., 5, p. 133; 1908 (S. P. 94). 

204. A Method of Producing Feebly Damped High-Fre¬ 

quency Electrical Oscillations for Laboratory 
Measurements; L. W. Austin, Bull., 5, p. 149; 
1908 (S. P. 95). 

205. The Comparative Sensitiveness of Some Common 

Detectors of Electrical Oscillations; L. W. 
Austin; Bull., 6, p. 527; 1910 (S. P. 140). 

206. The Measurement of Electric Oscillations in the 

Receiving Antenna; L. W. Austin; Bull., 7, p. 
295; 1911 (S. P. 157). 

207. Some Experiments with Coupled High-Frequency 

Circuits; L. W. Austin; Bull., 7, p. 301; 1911 (S. 
P. 158). 

208. On the Advantages of a High Spark Frequency in 

Radiotelegraphy; L. W. Austin; Bull., 5, p. 153; 
1908 (S. P. 96). 

209. Some Quantitative Experiments in Long Distance 

Radiotelegraphy; L. W. Austin; Bull., 7, p. 315; 

1911 (S. P. 159). 

210. Antenna Resistance; L. W. Austin; Bull., 9, p. 65; 

1912 (S. P. 189). 

211. The Energy Losses in Some Condensers Used in 

High-Frequency Circuits; L. W. Austin; Bull., 
9, p. 73; (S. P. 190). 

212. Quantitative Experiments in Radiotelegraphic 

Transmission; L. W. Austin; Bull., 11, p. 69; 
1914 (S. P. 226). 

213. Note on Resistance of Radiotelegraphic Antennas; 

L. W. Austin; Bull., 12, p. 465; 1915 (S. P. 257). 





RADIO—GOD’S WONDERFUL GIFT 
TO HUMANITY 

By C. B. Cooper 

VICE-PRES. SHIP OWNERS , RADIO SERVICE 




















APPENDIX C 


Radio—God's Wonderful Gift to Humanity 

What it Means to America 

“Life's lesson is here with its fascination, 
In this wireless thing that since creation 
Has been laid away in nature's store, 
Awaiting for some one to open the door. 

“And when we hear our big spark thunder 
Sending our signals away off yonder, 

With the speed of the wings of light, 
Through rain or shine or darkest night, 

“Or when we hear our ear 'phones rapping 
And answering signal comes clear and 
snapping, 

We can't comprehend the wonder—the why, 
Of this thing harnessed 'twixt earth and sky. 

“And whys breed answers and whvs again 
Till we lose ourselves in the endless chain, 
And where it leads or where the end, 

Is beyond our powers to comprehend. 

267 


268 


APPENDICES 


“The wizards—the men in the lab., you know, 
First added plus X to y or 0, 

And nature revealed to him who sought, 

And wireless telegraph to man was brought. 

“And though this was added to that, until 
Man conquered and harnessed it to his will, 
There still remains the same old cry— 
What is the thing, where from, and why? 

“This selfsame question fills the pages 
Of all the books of all the ages. 

Question breeds question and question again, 
Creating more riddles for man’s weak brain. 

“And that’s what keeps alive the flame 
And makes us play life’s little game. 
Uncertainties are the zest of life, 
Knowledge of the finish stops the strife. 

“And we who delve in our little part 
Of nature’s laws in this new-found art, 

Must realize there’s a power and plan, 

And a God—a ruler of nature and man. 

“This ‘Everything’ didn’t just happen to be; 
It must have been planned, created, and He 
Who planned and created must rule by right 
King of all nature—all man and all might. ’ ’ 


APPENDICES 


269 


Recently, in going through some old personal 
papers, I ran across the above—will I say poem? 
No, I think we had better call it simply rhyme 
because I am neither a poet nor a writer—but in 
reading it over I got to wondering if the thou¬ 
sands of people who are to-day thinking and talk¬ 
ing Radio, and who are nightly listening-in to the 
concerts being broadcasted by radio telephone, 
are thinking of the subject purely from a commer¬ 
cial standpoint, or from an amusement standpoint, 
or whether they really get the wonder of it all. 
The above rhyme was written a number of years 
ago after I had just finished the construction of a 
radio telegraph station in Alaska. I had sat in 
that station, surrounded by rocks and wilderness, 
listening to the pound of the waves on the shore, 
yet talking through space to the ships at sea. 

The apparatus that we were then using was of 
what is called the old “open spark type” that 
caused a noise like a gatling-gun. To-day the 
equipments have been perfected so that they are 
practically noiseless. 

At the time this verse was written there was no 
such thing as a radio law. Wireless telephone had 
not been thought of. We who were engaged in the 
business had not much in the way of apparatus, 
but we had ideals and vision. 

When we think of an ordinary telegraph mes¬ 
sage or a telephone message, we think of it as a 


270 


APPENDICES 


man-made something. We know that the message 
has been transmitted over man-made wires and 
man-made telegraph or telephone lines. The mes¬ 
sage itself has been received on man-made instru¬ 
ments, and our thought is of the cleverness and 
ability of the engineers who made it possible. But 
in thinking of a radio telephone or telegraph mes¬ 
sage, I, for one, always think of it not as man¬ 
made, but as God-given. 

It is true we have the man-made transmitting 
and the man-made receiving instruments, and we 
think of the wonderful cleverness of those who 
designed and built them, but the impulse trans¬ 
mitted and received travels through God’s air— 
through that life sustaining, almost unexplainable 
thing that we breathe, and I think of radio as a 
something that is not meant for man-made com¬ 
mercialism, but a God-given gift put into the 
world to accomplish the things that man-made 
equipments cannot accomplish. 

No other medium has yet been heard of that 
will communicate between ship and ship, or be¬ 
tween ship and shore. Therefore the Almighty 
undoubtedly meant the radio telegraph for this 
particular purpose. It is for the saving of lives, 
for the furtherance of the commercial handling 
of ships, and for the many benefits and comforts 
that it gives to those who travel the seas. 

Likewise, we now have the radio telephone. No 


APPENDICES 271 

other medium known will broadcast as it does, 
therefore is it not something that was given us 
primarily for that specific purpose? This must 
be seriously considered because there are only a 
limited number of wave bands in the air, and 
these bands must be conserved and allotted by 
proper Governmental regulations for specific 
purposes. If the radio telegraph were promis¬ 
cuously used for point to point service ashore the 
air would become clogged with messages to the 
extent that it would react against efficient ship 
communication. Likewise, if the radio telephone is 
promiscuously used for point to point, or ship and 
ship telephone communication, the air will become 
so clogged that it will react against the usefulness 
of broadcasting. 

For communication with ships we have the 
radio telegraph. For broadcasting we have the 
radio telephone. For point to point service on land 
we have the wire telegraph and telephone. Some 
day the radio art may be developed to a point 
where interference can be positively controlled, 
but until such time as this can be accomplished 
the Government will do well to guide the use of 
radio to the end of protecting the two specific 
purposes mentioned as much as possible against 
interference by other radio uses. 

Radio broadcasting should be protected, ex¬ 
tended by our Government and the commercial 


272 


APPENDICES 


radio companies, and all engaged in the business 
should work harmoniously to the end of making 
radio broadcasting what God intended it to be. 

The picture I see shows thousands and thou¬ 
sands of young men and boys studying, working, 
experimenting and enjoying their nightly occupa¬ 
tion, of “listening-in,”—boys and young men that 
would probably be on the streets or otherwise 
occupied away from their homes. Time after time 
I have had fathers and mothers speak to me of 
the fact that their boys were now spending their 
evenings at home where formerly their evenings 
were spent outside. This in itself, will undoubt¬ 
edly prove something that will be of untold benefit 
to the manhood of our country. 

I can also picture the day when every farm¬ 
house in the country will be equipped with radio 
receiving sets, and either the Government or 
commercial organizations will be transmitting con¬ 
certs, educational matter, together with weather 
reports or other information. To my mind this 
should mean a wonderful thing for the family 
situated miles from the railroad station, miles 
from the town, way off from those things that we 
of the city can enjoy, but which through the 
medium of radio broadcasting can be taken to the 
entire country, farmer and city dweller alike. 

Take the educational feature alone—is it not 
going to mean a broadening of the entire educa- 



APPENDICES 273 

tional system of the country? And when I say 
education I not only mean school and college in¬ 
formation, but I mean the discussion by prominent 
men of topics of the day, and as the rhyme says— 

“And where it leads or where the end 
Is beyond our powers to comprehend. * ’ 

Recently I sat in Washington and listened to 
the representative of a large corporation talk as 
though he thought the Government should turn 
the entire broadcasting control to his company, but 
I cannot imagine any Government doing anything 
that will permit a monopoly of this God-given 
something that can carry itself eventually into 
practically every home in the country. Our Gov¬ 
ernment must at all times keep itself in full con¬ 
trol,—should open the art to competition so that 
the best possible equipments will, by competition, 
be put at the disposal of the public, and Govern¬ 
ment regulations should go still farther and create 
control of the subject matter that is broadcasted, 
because the same medium that can be made so 
wonderfully useful can, at the same time, be put to 
equally harmful use. 

Supposing unrestricted broadcasting had ex¬ 
isted during or previous to the war. Suppose 
right now Bolshevists, Anarchists, or any indi¬ 
vidual or individuals were permitted to freely 


274 


APPENDICES 


broadcast uncensored ideas, our whole country 
could have been or could now be turned into tur¬ 
moil overnight. 

The ideal that should be striven for in the 
handling of both radio telegraph and radio tele¬ 
phone by Government, commercial, and general 
public alike, should be that 

“We who delve in our little part 
Of nature ’s laws in this new-found art, 

Must realize there’s a power and plan 
And a God—a ruler of nature and man. 

“ This * Everything’ didn’t just happen to be; 

It must have been planned, created, and he 
Who planned and created must rule by right 
King of all nature—all man and all might .’ 9 

Then let us endeavor to so draft our laws and so 
handle our business that this thing called Radio 
can be used for its God-given purpose of creating 
harmony, knowledge and brotherly love through¬ 
out the nation and throughout the oceans. 


INDEX 











\ 




INDEX 


A 

Abbreviations, 247 
Absorption, 165 
Alexanderson, 7, 101 
Alternating Current, 55, 172, 
173, 196 

Alternators, 7, 56,101, 183 
Ammeter, 165 
Ammeter, Hotwire, 165 
Ampere, 189 
Ampere-hour, 189 
Amplifiers, 144, 166 
Amplification, 144, 166 
Answers (Questions), 193 
Antennae, 157, 166, 167, 204, 
206 

Arc, 105, 168 
Arc Transmitters, 105 
Armstrong, 9, 146, 149 
Appendices, 228 
Attenuation, 169 
Audibility, 169 
Audion, 11 

Audion-Ultra, 127, 148 
Autodyne, 149 

B 

Batteries, Charging, 39-44 
Batteries, Dry, 29-31 
Batteries, Gravity, 26-29 

277 


Batteries, Storage, 31-44 
Batteries, Wet, 26-29 
Branley-Lodge, 2 
Braun, 4, 5 

Brush discharge or losses, 170 
C 

Cells, Charging, 39-44 
Cells, Dry, 29-31 
Cells, Gravity, 26-29 
Cells, Edison, 31-44 
Cells, Lead, 31-44 
Cells, Wet, 26-29 
Changer, Frequency, 170 
Changer, Wave, 170 
Charging Batteries, 39, 44 
Chopper, 184 
Circuits, Receiving, 117 
Code (Morse), 248 
Coherer, 2, 171 
Coils, 114 

Compass, Radio, 157, 171 
Conductance, 18-21 
Conductors, 18-21, 22, 23 
Condensers, 70, 114, 171, 191, 
202 

Corona, 170, 171 
Coulomb, 189 
Counterpoise, 163, 172 
Coupler, 172 
Coupling, 172, 202, 207 


278 


INDEX 


Crystal Detectors, 109 
Current, 55, 172, 173, 191 

D 

Damped Waves, 64, 79 
Damping, 94 
Decrement, 94, 205 
Definitions, 165 
Della Riccia, 4 
Detectors, Crystal, 109, 174 
Dry Batteries, 29, 31 
Ducretel, 4 

E 

Edison, 8 

Edison Batteries, 31-44 
Edison Effect, 8 
Efficiency, Over-all, 97 
Electrical Symbols, 10 
Electricity, 11-44 
Electrical Control, 21, 22 
Electricity, Source of, 24, 25 
Electro-Magnetism, 45-57 
Electrostatic Lines of Force, 
45-57, 189 

Electromotive Force, 24-44 
Electromotive Force, Induced, 
51-52 

Elementary Electricity, 11-44 
Excitation, Impulse, 98, 175 
Explanation of Radio, 56-63 

F 

Farad, 189 
Faults, 196 

Feed-back Circuit, 9,146, 149 


Fessenden, 6 

Fire Protection Laws, 228 
Fleming, 3, 8, 9 
Fleming Valve, 8, 9, 127 
Frequency, 5, 176, 187, 195, 
203 

G 

Gaps, Spark, 70, 184 
German Silver, 20 
Gravity Cells, 26, 29 
Grounds, 163 

H 

Henry, 189 
Hertz, 1, 2, 3 

Heterodyne Receiver, 149, 185 
History of Radio, 1-9 

I 

Induced emf., 51, 52 
Insulators, 23, 24 
Interference, 178 
Impedance, 189 
Impulse Transmitters, 98, 175 
Ionization, 131 


Kenetron, 134, 185 
Kilowatt, 191 

L 

Laws, Fire Protection, 228 


INDEX 


279 


Laws, Radio, 234 
Lead Cells, 31-44 
Length, Wave, 59-61 
Lightning Switch, 205 
Lines of Force, Electrostatic, 
45-57 

Lines of Force, Magnetic, 
Lodge, 3, 98 

M 

Magnetism, 45-57 
Magnetism, Electro-, 45-57, 
189 

Magnetite, 45 

Magnetic Lines of Force, 45- 
57, 189 

Marconi, 1, 2, 3, 4 
Meter, Wave, 183 
Morse Code, 248 
Modulation, Voice, 151 

N 

Nobel, 5 

Non-conductors, 23 
Non-synchronous Gaps, 75, 
184 

0 

Ohm, 189 

Oscillator, Arc, 168 
Oscillation Transformer, 190 

P 


Pliotron, 133, 185 
Potentiometer, 178 
Poulsen, 7 
Pupin, 4 

Q 

Quenched Gaps, 70, 184 
Questions and Answers, 193 

R 

Radio, Explanation of, 56-63 
Radio History, 1-9 
Radio Laws and Regulations, 
234 

Radio Reception, 109 
Radio Telephony, 151 
Reactance, 189, 190 
Reactance Coil, 190 
Receivers, 109, 211 
Receivers, Telephone, 112 
Receiving Circuits, 117 
Receiving Coils, 114 
Receiving Condensers, 114 
Receiving Tuners, 116 
Regenerative Circuit, 149 
Rectifiers, 109, 174, 179 
Relay, 179 

Resistance, 18-21, 180 
Resistors, 21, 22 
Resonance, 63, 180 
Rheostats, 21, 22, 190 
Right-hand Rule, 48, 49 
Rotary Gaps, 77, 184 


Period, 187 


Static, 181 


S 


280 


INDEX 


Selectivity, 191 
Silver, German, 20 
Source of Electricity, 24, 25 
Spark Gaps, 70, 202 
Stone, 4 

Storage Batteries, 31, 44 
Symbols, Electrical, 10 
Synchronous Gaps, 77, 184 

T 

Telefunken, 6 
Telephony, 151 
Telephone Receivers, 112, 207 
Tesla, 4 

Three-electrode Vacuum 
Tubes, 134 

Thompson Transmitter, 98 
Tikker, 185 
Trains, Wave, 62 
Transformer, 182 
Transmitters, Arc, 105 
Transmitters, 64, 79, 98, 101 
Trouble Finding, 196 
Tubes, Vacuum, 8, 9, 127 
Tuners, Receiving, 116 
Tungar Tube, 134 


Tuning, Undamped, 107 
Tuning, Damped, 88 
Two-electrode Vacuum Tubes, 
127 

U 

Undamped Receivers, 148 
Undamped Transmitters, 101 
Undamped Waves, 101 
Underwriters, Fire, 228 
United States Radio Laws, 
234 

V 

Vacuum Tubes, 8, 9, 127, 208 
Valve, Fleming, 8, 9, 127 
Voice Modulation, 151 
Volt, 189 

W 

Watt, 189 

Wave Length, 59, 61 
Wave Length Changes, 95 
Wavemeter, 184, 192 























